Cleveland Clinic Journal of Medicine

Our remarkable progress in understanding progressive multifocal leukoencephalopathy (PML) since its discovery more than 50 years ago has evolved in three stages, concurrent with the changing epidemiology of PML: the pre–human immunodeficiency virus (HIV) era; the HIV era, with highly active antiretroviral therapy (HAART) bringing further change; and the biologic therapy era.

Before the appearance of HIV, PML developed mostly in patients who had lymphoma, other malignancies, and rare forms of immunosuppression. The development of HIV changed the nature of PML, with more than 75% of cases now reported in HIV-infected patients. Within the HIV population, the epidemiology and prognosis of PML have undergone additional changes since the late 1990s. The introduction of HAART transformed PML from an almost uniformly fatal and inexorably progressive disease to one in which long-term survival is expected, particularly in the setting of robust immune reconstitution.¹

The third and most recent stage in the evolution of PML and our understanding of it has coincided with the introduction and use of increasingly potent immunosuppressive regimens and novel biologic immunologic therapies that target various aspects of the integrated immune response. These agents are being applied not only in the field of autoimmune and autoinflammatory disease but also in transplantation and oncology.

Collectively, vulnerable populations (ie, patients with lymphoreticular malignancies and autoinflammatory diseases) are now being subjected to therapies that singly or in combination have unknown effects on the immune system. As a byproduct, practitioners who were only vaguely aware of PML in the past now must consider PML in their differential diagnosis, develop a rational plan for evaluating such patients, and recognize when referral to a specialist is indicated. Recent descriptions of atypical forms of PML^2,3 add to the challenge for clinicians, as do reports of cases of PML in patients with minimal immunosuppression, in the absence of immunosuppressive therapy, and in patients who appear to have “normal” immune systems but in fact have diseases such as sarcoidosis.⁴ Rare cases are also being reported in patients with advanced liver disease.⁴

This article offers recommendations for enhanced awareness of PML, suggestions for improved evaluation of predisposed patients, and a summary of currently accepted treatment strategies.

WHEN TO SUSPECT PML

Patients being treated with immunosuppressive biologic agents represent a significant group that is predisposed to PML. At one time, focal neurologic deficits were required to consider the possibility of PML, but cognitive/behavioral abnormalities rather than focal neurologic findings are often the presenting sign in individuals treated with immune-modulating biologic agents. This phenomenon is most strikingly observed in recipients of natalizumab. Any central nervous system (CNS) dysfunction in a patient taking an immunosuppressive biologic agent should arouse suspicion for PML.

Peripheral neuropathy is not caused by PML but can coexist with it. Accordingly, in patients with rheumatologic disease who are receiving immune modifiers, neuromuscular symptoms in the absence of brain abnormalities on magnetic resonance imaging (MRI) argue against consideration of PML but do not rule it out—especially in patients with connective tissue diseases.

Systemic lupus erythematosus (SLE) represents a special challenge for several reasons. First, SLE appears to be a predisposing factor among other connective tissue diseases.⁵ In addition, SLE is associated with a variety of CNS complications, including a spectrum of focal and diffuse signs and symptoms that can mimic PML and lead to underdiagnosis.

Underrecognition is a risk in the HIV population as well, where cognitive impairment is common. Irrespective of immune or virologic status, 57% of HIV patients demonstrate impairment on neuropsychiatric testing. Often, mild to moderate cognitive impairment in HIV is attributed to HIV encephalopathy with no further workup, resulting in a missed or late diagnosis of PML.

IMAGING CONSIDERATIONS

In the rheumatologic disease population, especially those with SLE, and the HIV population, neuroimaging is indicated in any patient who presents with cognitive impairment. Typical radiographic characteristics of PML on MRI are subcortical white matter hyperintense areas on T2-weighted images and fluid-attenuated inversion recovery. T1-weighted images will reveal hypointense lesions that usually do not enhance, but may do so in fewer than 10% of patients with PML. Typically, no mass effect is seen.

In addition to rare faint gadolinium enhancement of lesions, other lesion characteristics may depart from the classic picture—for example, white matter and gray matter involvement, and monofocal instead of multifocal lesions. In HIV-positive patients, MRI can demonstrate diffuse cerebellar atrophy and subtle white matter abnormalities within the cerebellum.

Unfortunately, nonspecific white matter lesions occur in HIV infection as well as connective tissue diseases, compromising diagnostic specificity of a single imaging study. Nevertheless, progression of clinical signs and symptoms and progressive MRI changes should prompt a more vigorous diagnostic evaluation for PML. Alternatively, a normal MRI in a patient in whom PML is suspected has strong negative predictive value. In either situation, baseline neuroimaging is not recommended.

A neurology consult is advised when a patient has a predisposing condition for PML or suspicious neurologic signs or symptoms, whether focal or diffuse, and in whom an MRI demonstrates white matter changes.

Evaluation for JC virus DNA

When the neurology consult has been scheduled, and before the actual visit to the neurologist, a cerebrospinal fluid (CSF) sample should be obtained and evaluated for JC virus (JCV) DNA using a highly sensitive polymerase chain reaction (PCR) assay. Lumbar puncture in the setting of possible PML is critical to exclude the presence of other opportunistic infections.

The importance of using ultrasensitive PCR assays for diagnosing PML cannot be overstated, as falsely negative CSF PCR has been observed for JCV DNA despite high levels of JCV DNA in spinal fluid when utilizing less sensitive assays. The most sensitive commercial assays can detect as few as 50 copies of JCV DNA per mL of CSF fluid.

The risk of PML imparted by biologic agents other than natalizumab and nonbiologic immunosuppressive agents has been difficult to quantify, but no immune-modifying drug or combination of drugs appears entirely free of risk. Any patient who has had significant or prolonged immunosuppression should be considered vulnerable, and any patient with suspicion of PML based on unexplained neurologic symptoms warrants CSF examination for JCV DNA.

Brain biopsy

In patients with progressive clinical and MRI findings that suggest PML, but whose CSF PCR for JCV DNA is repeatedly negative, a brain biopsy is appropriate regardless of background immunosuppression. In the patient with rheumatologic disease, for example, suspicion of PML should be heightened if there is neurologic deterioration in the face of escalating antiinflammatory or immunosuppressive therapy for immune-driven inflammatory disease. Diagnostic urgency is particularly warranted in those disorders where the possibility for immune reconstitution is highest (ie, those receiving immunosuppressive regimens).

PML MANAGEMENT DEPENDS ON CLINICAL SETTING

Management of PML starts with risk stratification to identify those patients most prone to developing PML based on their immune status; the presence of autoimmune disease; the subtype of disease (in the case of SLE); and the nature, intensity, and duration of their immunosuppression. If a high-risk patient develops signs and symptoms of PML, the diagnosis should be anticipated and serious consideration given to withholding immunosuppressive therapies while the patient is being worked up.

Accelerating immune reconstitution

Once a diagnosis of PML is confirmed, immune reconstitution should be accelerated whenever possible. This can include temporary or permanent withdrawal of immunosuppressive therapy and initiation of plasmapheresis. Evidence supports continuing plasma exchange until natalizumab serum drug levels decline to less than 1 μg/mL to achieve desaturation of the alpha-4 integrin receptor.⁶ Typically, desaturation of the targeted integrin receptor occurs after five plasmapheresis sessions.

Immune reconstitution may also precipitate a syndrome known as the immune reconstitution inflammatory syndrome (IRIS), characterized by enlargement and contrast enhancement of PML lesions, appearance of new brain lesions, and worsening of neurologic deficits. The infiltration of the brain with inflammatory multinucleated cells and lymphocytes following abrupt immune reconstitution requires treatment. Opinion suggests that judicious use of corticosteroids may control the immune response in the brain in patients with PML-IRIS,^7,8 although further studies are needed.

Involving the patient in treatment decisions

Because risk tolerance varies considerably among individuals, patients should be informed of the risks of PML on the basis of their disease and the agents used to treat it. They should also be given information about the effects of individual treatments on the course of their disease, and they should be encouraged to participate in the selection of therapy.

SUMMARY

The approach to PML in the biologic era starts with an increased awareness of the disease followed by recognition of vulnerable populations and factors that contribute to the development of PML, such as biologic and nonbiologic immunosuppressive therapy. Optimal management includes a low threshold for investigating neurologic signs and symptoms and new-onset signs and symptoms in vulnerable populations, the use of MRI to detect typical PML brain lesions and other atypical brain features (ie, cerebellar atrophy), lumbar puncture and spinal CSF analysis to detect JCV DNA, and timely neurologic consultation for further evaluation. Much still needs to be learned about PML and the risks imparted by background diseases and individual drugs used in rheumatologic, neurologic, and oncologic disease.

Our remarkable progress in understanding progressive multifocal leukoencephalopathy (PML) since its discovery more than 50 years ago has evolved in three stages, concurrent with the changing epidemiology of PML: the pre–human immunodeficiency virus (HIV) era; the HIV era, with highly active antiretroviral therapy (HAART) bringing further change; and the biologic therapy era.

Before the appearance of HIV, PML developed mostly in patients who had lymphoma, other malignancies, and rare forms of immunosuppression. The development of HIV changed the nature of PML, with more than 75% of cases now reported in HIV-infected patients. Within the HIV population, the epidemiology and prognosis of PML have undergone additional changes since the late 1990s. The introduction of HAART transformed PML from an almost uniformly fatal and inexorably progressive disease to one in which long-term survival is expected, particularly in the setting of robust immune reconstitution.¹

The third and most recent stage in the evolution of PML and our understanding of it has coincided with the introduction and use of increasingly potent immunosuppressive regimens and novel biologic immunologic therapies that target various aspects of the integrated immune response. These agents are being applied not only in the field of autoimmune and autoinflammatory disease but also in transplantation and oncology.

Collectively, vulnerable populations (ie, patients with lymphoreticular malignancies and autoinflammatory diseases) are now being subjected to therapies that singly or in combination have unknown effects on the immune system. As a byproduct, practitioners who were only vaguely aware of PML in the past now must consider PML in their differential diagnosis, develop a rational plan for evaluating such patients, and recognize when referral to a specialist is indicated. Recent descriptions of atypical forms of PML^2,3 add to the challenge for clinicians, as do reports of cases of PML in patients with minimal immunosuppression, in the absence of immunosuppressive therapy, and in patients who appear to have “normal” immune systems but in fact have diseases such as sarcoidosis.⁴ Rare cases are also being reported in patients with advanced liver disease.⁴

This article offers recommendations for enhanced awareness of PML, suggestions for improved evaluation of predisposed patients, and a summary of currently accepted treatment strategies.

WHEN TO SUSPECT PML

Patients being treated with immunosuppressive biologic agents represent a significant group that is predisposed to PML. At one time, focal neurologic deficits were required to consider the possibility of PML, but cognitive/behavioral abnormalities rather than focal neurologic findings are often the presenting sign in individuals treated with immune-modulating biologic agents. This phenomenon is most strikingly observed in recipients of natalizumab. Any central nervous system (CNS) dysfunction in a patient taking an immunosuppressive biologic agent should arouse suspicion for PML.

Peripheral neuropathy is not caused by PML but can coexist with it. Accordingly, in patients with rheumatologic disease who are receiving immune modifiers, neuromuscular symptoms in the absence of brain abnormalities on magnetic resonance imaging (MRI) argue against consideration of PML but do not rule it out—especially in patients with connective tissue diseases.

Systemic lupus erythematosus (SLE) represents a special challenge for several reasons. First, SLE appears to be a predisposing factor among other connective tissue diseases.⁵ In addition, SLE is associated with a variety of CNS complications, including a spectrum of focal and diffuse signs and symptoms that can mimic PML and lead to underdiagnosis.

Underrecognition is a risk in the HIV population as well, where cognitive impairment is common. Irrespective of immune or virologic status, 57% of HIV patients demonstrate impairment on neuropsychiatric testing. Often, mild to moderate cognitive impairment in HIV is attributed to HIV encephalopathy with no further workup, resulting in a missed or late diagnosis of PML.

IMAGING CONSIDERATIONS

In the rheumatologic disease population, especially those with SLE, and the HIV population, neuroimaging is indicated in any patient who presents with cognitive impairment. Typical radiographic characteristics of PML on MRI are subcortical white matter hyperintense areas on T2-weighted images and fluid-attenuated inversion recovery. T1-weighted images will reveal hypointense lesions that usually do not enhance, but may do so in fewer than 10% of patients with PML. Typically, no mass effect is seen.

In addition to rare faint gadolinium enhancement of lesions, other lesion characteristics may depart from the classic picture—for example, white matter and gray matter involvement, and monofocal instead of multifocal lesions. In HIV-positive patients, MRI can demonstrate diffuse cerebellar atrophy and subtle white matter abnormalities within the cerebellum.

Unfortunately, nonspecific white matter lesions occur in HIV infection as well as connective tissue diseases, compromising diagnostic specificity of a single imaging study. Nevertheless, progression of clinical signs and symptoms and progressive MRI changes should prompt a more vigorous diagnostic evaluation for PML. Alternatively, a normal MRI in a patient in whom PML is suspected has strong negative predictive value. In either situation, baseline neuroimaging is not recommended.

A neurology consult is advised when a patient has a predisposing condition for PML or suspicious neurologic signs or symptoms, whether focal or diffuse, and in whom an MRI demonstrates white matter changes.

Evaluation for JC virus DNA

When the neurology consult has been scheduled, and before the actual visit to the neurologist, a cerebrospinal fluid (CSF) sample should be obtained and evaluated for JC virus (JCV) DNA using a highly sensitive polymerase chain reaction (PCR) assay. Lumbar puncture in the setting of possible PML is critical to exclude the presence of other opportunistic infections.

The importance of using ultrasensitive PCR assays for diagnosing PML cannot be overstated, as falsely negative CSF PCR has been observed for JCV DNA despite high levels of JCV DNA in spinal fluid when utilizing less sensitive assays. The most sensitive commercial assays can detect as few as 50 copies of JCV DNA per mL of CSF fluid.

The risk of PML imparted by biologic agents other than natalizumab and nonbiologic immunosuppressive agents has been difficult to quantify, but no immune-modifying drug or combination of drugs appears entirely free of risk. Any patient who has had significant or prolonged immunosuppression should be considered vulnerable, and any patient with suspicion of PML based on unexplained neurologic symptoms warrants CSF examination for JCV DNA.

Brain biopsy

In patients with progressive clinical and MRI findings that suggest PML, but whose CSF PCR for JCV DNA is repeatedly negative, a brain biopsy is appropriate regardless of background immunosuppression. In the patient with rheumatologic disease, for example, suspicion of PML should be heightened if there is neurologic deterioration in the face of escalating antiinflammatory or immunosuppressive therapy for immune-driven inflammatory disease. Diagnostic urgency is particularly warranted in those disorders where the possibility for immune reconstitution is highest (ie, those receiving immunosuppressive regimens).

PML MANAGEMENT DEPENDS ON CLINICAL SETTING

Management of PML starts with risk stratification to identify those patients most prone to developing PML based on their immune status; the presence of autoimmune disease; the subtype of disease (in the case of SLE); and the nature, intensity, and duration of their immunosuppression. If a high-risk patient develops signs and symptoms of PML, the diagnosis should be anticipated and serious consideration given to withholding immunosuppressive therapies while the patient is being worked up.

Accelerating immune reconstitution

Once a diagnosis of PML is confirmed, immune reconstitution should be accelerated whenever possible. This can include temporary or permanent withdrawal of immunosuppressive therapy and initiation of plasmapheresis. Evidence supports continuing plasma exchange until natalizumab serum drug levels decline to less than 1 μg/mL to achieve desaturation of the alpha-4 integrin receptor.⁶ Typically, desaturation of the targeted integrin receptor occurs after five plasmapheresis sessions.

Immune reconstitution may also precipitate a syndrome known as the immune reconstitution inflammatory syndrome (IRIS), characterized by enlargement and contrast enhancement of PML lesions, appearance of new brain lesions, and worsening of neurologic deficits. The infiltration of the brain with inflammatory multinucleated cells and lymphocytes following abrupt immune reconstitution requires treatment. Opinion suggests that judicious use of corticosteroids may control the immune response in the brain in patients with PML-IRIS,^7,8 although further studies are needed.

Involving the patient in treatment decisions

Because risk tolerance varies considerably among individuals, patients should be informed of the risks of PML on the basis of their disease and the agents used to treat it. They should also be given information about the effects of individual treatments on the course of their disease, and they should be encouraged to participate in the selection of therapy.

SUMMARY

The approach to PML in the biologic era starts with an increased awareness of the disease followed by recognition of vulnerable populations and factors that contribute to the development of PML, such as biologic and nonbiologic immunosuppressive therapy. Optimal management includes a low threshold for investigating neurologic signs and symptoms and new-onset signs and symptoms in vulnerable populations, the use of MRI to detect typical PML brain lesions and other atypical brain features (ie, cerebellar atrophy), lumbar puncture and spinal CSF analysis to detect JCV DNA, and timely neurologic consultation for further evaluation. Much still needs to be learned about PML and the risks imparted by background diseases and individual drugs used in rheumatologic, neurologic, and oncologic disease.

Our remarkable progress in understanding progressive multifocal leukoencephalopathy (PML) since its discovery more than 50 years ago has evolved in three stages, concurrent with the changing epidemiology of PML: the pre–human immunodeficiency virus (HIV) era; the HIV era, with highly active antiretroviral therapy (HAART) bringing further change; and the biologic therapy era.

Before the appearance of HIV, PML developed mostly in patients who had lymphoma, other malignancies, and rare forms of immunosuppression. The development of HIV changed the nature of PML, with more than 75% of cases now reported in HIV-infected patients. Within the HIV population, the epidemiology and prognosis of PML have undergone additional changes since the late 1990s. The introduction of HAART transformed PML from an almost uniformly fatal and inexorably progressive disease to one in which long-term survival is expected, particularly in the setting of robust immune reconstitution.¹

The third and most recent stage in the evolution of PML and our understanding of it has coincided with the introduction and use of increasingly potent immunosuppressive regimens and novel biologic immunologic therapies that target various aspects of the integrated immune response. These agents are being applied not only in the field of autoimmune and autoinflammatory disease but also in transplantation and oncology.

Collectively, vulnerable populations (ie, patients with lymphoreticular malignancies and autoinflammatory diseases) are now being subjected to therapies that singly or in combination have unknown effects on the immune system. As a byproduct, practitioners who were only vaguely aware of PML in the past now must consider PML in their differential diagnosis, develop a rational plan for evaluating such patients, and recognize when referral to a specialist is indicated. Recent descriptions of atypical forms of PML^2,3 add to the challenge for clinicians, as do reports of cases of PML in patients with minimal immunosuppression, in the absence of immunosuppressive therapy, and in patients who appear to have “normal” immune systems but in fact have diseases such as sarcoidosis.⁴ Rare cases are also being reported in patients with advanced liver disease.⁴

This article offers recommendations for enhanced awareness of PML, suggestions for improved evaluation of predisposed patients, and a summary of currently accepted treatment strategies.

WHEN TO SUSPECT PML

Patients being treated with immunosuppressive biologic agents represent a significant group that is predisposed to PML. At one time, focal neurologic deficits were required to consider the possibility of PML, but cognitive/behavioral abnormalities rather than focal neurologic findings are often the presenting sign in individuals treated with immune-modulating biologic agents. This phenomenon is most strikingly observed in recipients of natalizumab. Any central nervous system (CNS) dysfunction in a patient taking an immunosuppressive biologic agent should arouse suspicion for PML.

Peripheral neuropathy is not caused by PML but can coexist with it. Accordingly, in patients with rheumatologic disease who are receiving immune modifiers, neuromuscular symptoms in the absence of brain abnormalities on magnetic resonance imaging (MRI) argue against consideration of PML but do not rule it out—especially in patients with connective tissue diseases.

Systemic lupus erythematosus (SLE) represents a special challenge for several reasons. First, SLE appears to be a predisposing factor among other connective tissue diseases.⁵ In addition, SLE is associated with a variety of CNS complications, including a spectrum of focal and diffuse signs and symptoms that can mimic PML and lead to underdiagnosis.

Underrecognition is a risk in the HIV population as well, where cognitive impairment is common. Irrespective of immune or virologic status, 57% of HIV patients demonstrate impairment on neuropsychiatric testing. Often, mild to moderate cognitive impairment in HIV is attributed to HIV encephalopathy with no further workup, resulting in a missed or late diagnosis of PML.

IMAGING CONSIDERATIONS

In the rheumatologic disease population, especially those with SLE, and the HIV population, neuroimaging is indicated in any patient who presents with cognitive impairment. Typical radiographic characteristics of PML on MRI are subcortical white matter hyperintense areas on T2-weighted images and fluid-attenuated inversion recovery. T1-weighted images will reveal hypointense lesions that usually do not enhance, but may do so in fewer than 10% of patients with PML. Typically, no mass effect is seen.

In addition to rare faint gadolinium enhancement of lesions, other lesion characteristics may depart from the classic picture—for example, white matter and gray matter involvement, and monofocal instead of multifocal lesions. In HIV-positive patients, MRI can demonstrate diffuse cerebellar atrophy and subtle white matter abnormalities within the cerebellum.

Unfortunately, nonspecific white matter lesions occur in HIV infection as well as connective tissue diseases, compromising diagnostic specificity of a single imaging study. Nevertheless, progression of clinical signs and symptoms and progressive MRI changes should prompt a more vigorous diagnostic evaluation for PML. Alternatively, a normal MRI in a patient in whom PML is suspected has strong negative predictive value. In either situation, baseline neuroimaging is not recommended.

A neurology consult is advised when a patient has a predisposing condition for PML or suspicious neurologic signs or symptoms, whether focal or diffuse, and in whom an MRI demonstrates white matter changes.

Evaluation for JC virus DNA

When the neurology consult has been scheduled, and before the actual visit to the neurologist, a cerebrospinal fluid (CSF) sample should be obtained and evaluated for JC virus (JCV) DNA using a highly sensitive polymerase chain reaction (PCR) assay. Lumbar puncture in the setting of possible PML is critical to exclude the presence of other opportunistic infections.

The importance of using ultrasensitive PCR assays for diagnosing PML cannot be overstated, as falsely negative CSF PCR has been observed for JCV DNA despite high levels of JCV DNA in spinal fluid when utilizing less sensitive assays. The most sensitive commercial assays can detect as few as 50 copies of JCV DNA per mL of CSF fluid.

The risk of PML imparted by biologic agents other than natalizumab and nonbiologic immunosuppressive agents has been difficult to quantify, but no immune-modifying drug or combination of drugs appears entirely free of risk. Any patient who has had significant or prolonged immunosuppression should be considered vulnerable, and any patient with suspicion of PML based on unexplained neurologic symptoms warrants CSF examination for JCV DNA.

Brain biopsy

In patients with progressive clinical and MRI findings that suggest PML, but whose CSF PCR for JCV DNA is repeatedly negative, a brain biopsy is appropriate regardless of background immunosuppression. In the patient with rheumatologic disease, for example, suspicion of PML should be heightened if there is neurologic deterioration in the face of escalating antiinflammatory or immunosuppressive therapy for immune-driven inflammatory disease. Diagnostic urgency is particularly warranted in those disorders where the possibility for immune reconstitution is highest (ie, those receiving immunosuppressive regimens).

PML MANAGEMENT DEPENDS ON CLINICAL SETTING

Management of PML starts with risk stratification to identify those patients most prone to developing PML based on their immune status; the presence of autoimmune disease; the subtype of disease (in the case of SLE); and the nature, intensity, and duration of their immunosuppression. If a high-risk patient develops signs and symptoms of PML, the diagnosis should be anticipated and serious consideration given to withholding immunosuppressive therapies while the patient is being worked up.

Accelerating immune reconstitution

Once a diagnosis of PML is confirmed, immune reconstitution should be accelerated whenever possible. This can include temporary or permanent withdrawal of immunosuppressive therapy and initiation of plasmapheresis. Evidence supports continuing plasma exchange until natalizumab serum drug levels decline to less than 1 μg/mL to achieve desaturation of the alpha-4 integrin receptor.⁶ Typically, desaturation of the targeted integrin receptor occurs after five plasmapheresis sessions.

Immune reconstitution may also precipitate a syndrome known as the immune reconstitution inflammatory syndrome (IRIS), characterized by enlargement and contrast enhancement of PML lesions, appearance of new brain lesions, and worsening of neurologic deficits. The infiltration of the brain with inflammatory multinucleated cells and lymphocytes following abrupt immune reconstitution requires treatment. Opinion suggests that judicious use of corticosteroids may control the immune response in the brain in patients with PML-IRIS,^7,8 although further studies are needed.

Involving the patient in treatment decisions

Because risk tolerance varies considerably among individuals, patients should be informed of the risks of PML on the basis of their disease and the agents used to treat it. They should also be given information about the effects of individual treatments on the course of their disease, and they should be encouraged to participate in the selection of therapy.

SUMMARY

The approach to PML in the biologic era starts with an increased awareness of the disease followed by recognition of vulnerable populations and factors that contribute to the development of PML, such as biologic and nonbiologic immunosuppressive therapy. Optimal management includes a low threshold for investigating neurologic signs and symptoms and new-onset signs and symptoms in vulnerable populations, the use of MRI to detect typical PML brain lesions and other atypical brain features (ie, cerebellar atrophy), lumbar puncture and spinal CSF analysis to detect JCV DNA, and timely neurologic consultation for further evaluation. Much still needs to be learned about PML and the risks imparted by background diseases and individual drugs used in rheumatologic, neurologic, and oncologic disease.

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic infection of the central nervous system (CNS). Although originally associated with broad-based immunosuppression (human immunodeficiency virus infection, lymphoproliferative disorders, and immunosuppressive medications), recognition of PML in patients with selective immunosuppression is growing. This restricted immunodeviation can arise from autoimmune disorders such as systemic lupus erythematosus, selective immunosuppressive therapies (eg, rituximab, leflunomide, and efalizumab), or immunosuppression limited to the CNS (eg, treatment with natalizumab).

This article reviews approaches to the management of PML, with specific recommendations regarding PML associated with natalizumab therapy.

APPROACH TO PML TREATMENT

The ideal approach to PML treatment is generally two-pronged: antiviral therapies to directly reduce viral replication and immune reconstitution that empowers the immune system to attack the JC virus (JCV). Challenges to treatment are the difficulty in culturing JCV for in vitro studies, lack of an animal model of PML, and infrequency of PML cases.

Antiviral therapies

At present, no antiviral agent has confirmed efficacy in PML. Nucleoside analogues, serotonin 5-hydroxytryptamine receptor antagonists (to block the JCV receptor), and several cytokines provided exciting prospects in preclinical studies for treatment of PML in humans. Unfortunately, subsequent clinical studies of cytarabine, cidofovir, and interferon alfa all yielded disappointing results. A derivative of cidofovir, CMX001, is also being evaluated for efficacy in PML. Mefloquine was identified through a broad pharmaceutical screening study to have strong antiviral effects in vitro, but a clinical trial to assess its effects was stopped. It remains unclear whether the failure of clinical studies after successful in vitro studies is secondary to low drug penetration into the CNS, treatment initiation too late in the course of PML, or other differences not yet fully understood.

Immune reconstitution

Given the widespread failure of antiviral regimens, the mainstay of PML treatment is immune reconstitution. When immunosuppression is secondary to a medical disorder, efforts are pursued to reverse the primary disorder. For example, highly active antiretroviral therapy significantly prolongs survival in antiretroviral-naïve acquired immunodeficiency syndrome patients.^1,2 Decreasing the intensity of immunosuppressive therapy in solid organ transplant may improve survival with PML. When PML is associated with biologic therapies for autoimmune diseases, early diagnosis and immediate suspension of therapy is thought to improve outcomes.

EXPERIENCE WITH NATALIZUMAB

PML in the setting of natalizumab therapy is related to cumulative exposure to natalizumab. As of August 4, 2011, there had been 150 cases of natalizumab-related PML documented in more than 88,000 patients exposed to natalizumab worldwide³ (see page S18, “Multiple sclerosis, natalizumab, and PML: Helping patients decide”). The incidence of PML in natalizumab-treated patients varies according to the number of infusions received, but the incidence of PML by each epoch of treatment exposure (1 to 24 infusions, 25 to 36 infusions, 37 to 48 infusions) appears to have remained stable over time.³

The mortality associated with natalizumab-related PML was 19% (29 deaths among the 150 confirmed cases) as of August 4, 2011.³ In cases with at least 6 months of follow-up, mortality has remained at about 20%. Many who survived were left with serious morbidity and permanent disability, although interpretation of disability is difficult because functional impairment is a hallmark of multiple sclerosis (MS) irrespective of PML. Survival in patients with natalizumab-associated PML appears to be better than with PML associated with other conditions, possibly because of early diagnosis achieved through clinical vigilance and swift immune reconstitution through natalizumab discontinuation and either plasmapheresis or immunoabsorption. Predictors of survival include younger age at diagnosis, less disability prior to onset of PML, more localized disease on magnetic resonance imaging (MRI) of the brain, and shorter time from symptom onset to PML diagnosis.

Clinical characteristics of natalizumab-associated PML

Several clinical observations should increase suspicion of natalizumab-associated PML.^3–5 For example, the most common presenting symptoms are cognitive, motor, language, and visual impairment. Gadolinium-enhancing lesions are observed at presentation in about one-half of patients. Seizures and paroxysmal events can occur at presentation, which helps to differentiate PML from an MS relapse.

Approximately one-half of patients with natalizumab-associated PML have an initial viral load of less than 500 copies/mL, underscoring the need for ultrasensitive polymerase chain reaction (PCR) testing. An ultrasensitive JCV assay (Focus Diagnostics, Cypress, California) is available that can detect less than 50 copies/mL of JCV DNA. Because the viral copy numbers in the cerebrospinal fluid (CSF) may be low in patients treated with natalizumab, the CSF PCR may be falsely negative. In several cases of PML, JCV was undetectable in the CSF by PCR, identified only later by repeat PCR or brain biopsy.⁴ Serum JCV PCR is not useful in the screening or diagnosis of PML.

Natalizumab-associated PML has not been observed with therapy of 6 months’ or less duration. After 6 months of natalizumab therapy, new MRI lesions are rare in patients who are negative for neutralizing antibodies. A new MRI lesion in such a patient should be considered suspicious for PML. Our standard protocol is to check for neutralizing antibodies at 6 months in all patients treated with natalizumab. Symptoms of PML develop in affected patients whose duration of therapy ranges from 6 to 81 infusions. Symptoms often develop well before PML is diagnosed.^4,5

Forty-six percent of patients treated with natalizumab who develop PML have received previous autologous bone marrow transplantation or chemo therapy, including mitoxantrone, azathioprine, methotrexate, and mycophenolate mofetil. In comparison, up to 25% of MS patients who were treated with natalizumab (13% in the United States, 24% in Europe) have had prior chemotherapy treatment. Prior immunosuppressive therapy increases the risk of PML by two- to fourfold, which may explain the higher rate of PML in Europe compared with that of the United States.^4,5

Testing for immune response to JCV

A JCV enzyme-linked immunosorbent assay (ELISA) test has been developed that identifies patients with an immune response to JCV. Among MS patients, 55% test positive for JCV through this assay.⁶ The false-negative rate of the test is 5%, and the overall annual seroconversion rate is estimated to be about 2%, necessitating repeat testing.

Based on results of this assay, the estimated risk of PML in seropositive patients is about 1 in 500.⁶ The test was positive in 28 of 28 patients who developed PML. The probability of this relationship occurring by chance is 0.5528, which suggests that this assay is useful to stratify risk for development of PML. Although the rate of false negatives makes the test an imperfect predictor, it is still useful in clinical practice. The test became available clinically in late summer 2011. Further longitudinal observation studies (STRATIFY-1 and STRATIFY-2) on the use of the JCV ELISA to detect anti-JCV antibodies in the blood of natalizumab-treated patients with MS are under way.

Stratifying risk for natalizumab-related PML

The possibility of reducing the risk of PML in natalizumab-treated patients through natalizumab holidays is attractive. When exploring this option, one must consider whether the risk of recurrent disease activity with treatment interruption outweighs the potentially decreased risk of PML.⁸ A randomized controlled multicenter clinical trial of natalizumab interruption is ongoing, with the recruitment phase complete after enrollment of 175 patients. Patients taking natalizumab at study entry have been randomized to one of three arms: continuation of monthly natalizumab for 6 months, placebo for 6 months, or an alternate treatment (interferon beta-1a, glatiramer acetate, or monthly intravenous steroids) for 6 months administered open-label by clinician and patient choice.

The primary outcome measures are markers of immune function and overall disease activity during treatment interruption and after resumption. Patients are monitored monthly using MRI to measure disease activity. Those who experience relapse will have the option of returning to natalizumab therapy or switching to an alternate treatment. The results of this prospective, randomized, controlled trial will provide a greater understanding of the safety issues surrounding natalizumab holidays.

Management of natalizumab-related PML

Management of patients taking natalizumab starts with risk stratification in an attempt to prevent the development of PML. If suspicion for PML is raised based on symptoms, early diagnosis can be accomplished through the use of a sensitive JCV PCR assay, with a repeat PCR if negative. Natalizumab treatment should be withheld during the workup for PML.

Reprinted, with permission, from Neurology (Khatri BO, et al. Effect of plasma exchange in accelerating natalizumab clearance and restoring leukocyte function. Neurology 2009; 72:402–409).

When immunosuppression is rapidly reversed in cases of natalizumab-associated PML, an overly exuberant immune response targeting JCV in the CNS is observed 2 to 6 weeks later. The response, termed immune reconstitution inflammatory syndrome (IRIS), is not always easy to differentiate from progression of PML. Nonetheless, most clinicians recommend high-dose corticosteroids if a clinical and imaging syndrome resembling IRIS develops several weeks after immune restoration.¹⁰ The objective is to achieve the immune reconstitution needed to control JCV infection while limiting the collateral damage of inflammation on the remaining brain tissue.

SUMMARY

Risk factors for natalizumab-associated PML include duration of treatment with natalizumab, previous chemotherapy, and JCV antibody serology. Early diagnosis requires the use of an ultrasensitive JCV PCR assay. Treatment is focused on early diagnosis, immediate cessation of pharmacologic causes of immunosuppression, and active efforts to accelerate immune restoration.

DISCUSSION

Dr. Calabrese: What are your thoughts about plasmapheresis for rituximab-related cases of PML?

Dr. Fox: It’s probably not going to be as helpful as with natalizumab. Rituximab has pharmacokinetics that are similar to those of other monoclonal antibodies, with a half-life in the range of 14 to 20 days. So it’s pretty much absent from the body within 1 to 2 months of infusion. The enduring benefit from rituximab comes not from the persistent presence of the monoclonal antibody, but the persistent absence of CD19 B cells. Plasmapheresis is unlikely to be effective because it won’t accelerate return of CD19 B cells to the peripheral circulation. In rituximab-related PML, stimulating the bone marrow to produce more B cells in order to restore the immune system is more likely to be effective. In contrast, I did recommend plasma pheresis in a case of efalizumab-related PML. Because efalizumab is a binding antibody to the CD11a receptor, we wanted to accelerate its removal.

Dr. Molloy: In an MS patient who responds well to natalizumab, do you ever explore a strategy of dose reduction or extending the dosing interval of natalizumab?

Dr. Fox: Let me put that into a clinical context. A 35-year old man has had relapsing-remitting MS for 3 years. Two years ago, after disease activity occurred while he was using an injectable therapy, he started natalizumab and has been clinically and radiologically stable on natalizumab. Then, he gets the JCV assay, it’s positive, and he asks if it’s time to get off natalizumab “because of the risk of that brain virus.”

What do I tell him? Should I change the dosing interval? At this point, we are not doing either. One reason is the unpredictable pharmacokinetics of the drug. The dose and dosing regimen were chosen to have 85% or greater receptor saturation in 95% or more of patients over the course of the recommended 4-week dosing interval. If you increase the interval to 6 weeks or 8 weeks, you can’t predict in individual patients whether or not meaningful desaturation occurs and thus allows some immune cells to enter the brain to protect against PML (but not too many, or MS disease activity will return).

Dr. Simpson: Do you have an algorithm for working up patients?

Dr. Fox: It depends on the level of suspicion given the patient’s symptoms. It’s difficult to find a single MS patient who does not have some fluctuation of symptoms over time and some worsening of symptoms such as stiffness, fatigue, and cognitive difficulties. They all have changes in mood, so if one took any symptom change—any change in their report of mood and cognition— as the cutoff for a workup, we wouldn’t be giving natalizumab at all. But if a patient or family says, “I am worried,” then we need to work it up. Also, if there are clearcut new or worsening neurologic symptoms, we pursue a workup. Often, the change in symptoms is revealed when the patient comes in for his or her monthly infusion and the nurse asks the four questions from the preinfusion checklist (as part of the mandatory Tysabri Outreach: Unified Commitment to Health [TOUCH] prescribing program for natalizumab).¹¹

If there are new symptoms, we hold infusions and do a two-stage evaluation. The first stage is a brain MRI to evaluate for change from baseline (the US Food and Drug Administration requires a brain MRI at baseline before starting natalizumab therapy). Most patients undergo a brain MRI every 6 to 12 months while on natalizumab therapy, with instructions to the neuroradiologist to evaluate carefully for new lesions. In our institution, the PML MRI evaluation is a fine-toothcomb assessment of lesions from the most recent MRI compared with the current MRI. Depending on the results of the current MRI and on our level of suspicion, we may proceed to a spinal tap, even if the MRI findings are stable. We have done 8 to 10 spinal taps in patients taking natalizumab when we were suspicious enough to evaluate for PML. Occasional patients continue to have active disease, relapses, and new lesions even without developing antibodies while taking natalizumab.

Dr. Rudick: We need a quick, quantitative analysis method to compare one MRI with another. It is easy to say, “Consider PML if there are new lesions.” It’s not so easy to know if the lesions are new. We are participating in a National Institutes of Health study regarding identification of biomarkers of interferon’s effects, and the study requires obtaining MRI scans at baseline and 6 months. We have state-of-the-art subtraction MRI to quantify new lesions on the followup MRI. However, there is significant disagreement on the number of new lesions determined by clinical raters, and disagreement between the clinical raters and the numbers generated by the computer program.

Dr. Major: Is the incidence of natalizumab-related PML based on the number of months or on the number of infusions?

Dr. Fox: It is based on the number of infusions. You bring up a good point because these patients may interrupt treatment when they go on vacation, for example, or have a lapse in insurance coverage. Most patients follow the every-4-weeks protocol and receive 13 infusions in a year. Perhaps 10% to 15% do not follow it precisely.

Dr. Molloy: Is everyone who takes natalizumab being followed for PML even if they discontinue natalizumab? Have any differences emerged in the factors that predispose to PML among those who continue therapy compared with those who discontinue? I ask because I’m wondering why the incidence appears to stabilize, or even go down, after 36 infusions.

Dr. Fox: PML has not been reported beyond several months after stopping natalizumab; concern about PML can decrease fairly quickly after stopping the drug. Many of us expected the risk of PML to continue rising with cumulative treatment, so were pleasantly surprised to see a plateau in the risk of PML after about 36 months. We don’t understand what leads to this plateau.

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic infection of the central nervous system (CNS). Although originally associated with broad-based immunosuppression (human immunodeficiency virus infection, lymphoproliferative disorders, and immunosuppressive medications), recognition of PML in patients with selective immunosuppression is growing. This restricted immunodeviation can arise from autoimmune disorders such as systemic lupus erythematosus, selective immunosuppressive therapies (eg, rituximab, leflunomide, and efalizumab), or immunosuppression limited to the CNS (eg, treatment with natalizumab).

This article reviews approaches to the management of PML, with specific recommendations regarding PML associated with natalizumab therapy.

APPROACH TO PML TREATMENT

The ideal approach to PML treatment is generally two-pronged: antiviral therapies to directly reduce viral replication and immune reconstitution that empowers the immune system to attack the JC virus (JCV). Challenges to treatment are the difficulty in culturing JCV for in vitro studies, lack of an animal model of PML, and infrequency of PML cases.

Antiviral therapies

At present, no antiviral agent has confirmed efficacy in PML. Nucleoside analogues, serotonin 5-hydroxytryptamine receptor antagonists (to block the JCV receptor), and several cytokines provided exciting prospects in preclinical studies for treatment of PML in humans. Unfortunately, subsequent clinical studies of cytarabine, cidofovir, and interferon alfa all yielded disappointing results. A derivative of cidofovir, CMX001, is also being evaluated for efficacy in PML. Mefloquine was identified through a broad pharmaceutical screening study to have strong antiviral effects in vitro, but a clinical trial to assess its effects was stopped. It remains unclear whether the failure of clinical studies after successful in vitro studies is secondary to low drug penetration into the CNS, treatment initiation too late in the course of PML, or other differences not yet fully understood.

Immune reconstitution

Given the widespread failure of antiviral regimens, the mainstay of PML treatment is immune reconstitution. When immunosuppression is secondary to a medical disorder, efforts are pursued to reverse the primary disorder. For example, highly active antiretroviral therapy significantly prolongs survival in antiretroviral-naïve acquired immunodeficiency syndrome patients.^1,2 Decreasing the intensity of immunosuppressive therapy in solid organ transplant may improve survival with PML. When PML is associated with biologic therapies for autoimmune diseases, early diagnosis and immediate suspension of therapy is thought to improve outcomes.

EXPERIENCE WITH NATALIZUMAB

PML in the setting of natalizumab therapy is related to cumulative exposure to natalizumab. As of August 4, 2011, there had been 150 cases of natalizumab-related PML documented in more than 88,000 patients exposed to natalizumab worldwide³ (see page S18, “Multiple sclerosis, natalizumab, and PML: Helping patients decide”). The incidence of PML in natalizumab-treated patients varies according to the number of infusions received, but the incidence of PML by each epoch of treatment exposure (1 to 24 infusions, 25 to 36 infusions, 37 to 48 infusions) appears to have remained stable over time.³

The mortality associated with natalizumab-related PML was 19% (29 deaths among the 150 confirmed cases) as of August 4, 2011.³ In cases with at least 6 months of follow-up, mortality has remained at about 20%. Many who survived were left with serious morbidity and permanent disability, although interpretation of disability is difficult because functional impairment is a hallmark of multiple sclerosis (MS) irrespective of PML. Survival in patients with natalizumab-associated PML appears to be better than with PML associated with other conditions, possibly because of early diagnosis achieved through clinical vigilance and swift immune reconstitution through natalizumab discontinuation and either plasmapheresis or immunoabsorption. Predictors of survival include younger age at diagnosis, less disability prior to onset of PML, more localized disease on magnetic resonance imaging (MRI) of the brain, and shorter time from symptom onset to PML diagnosis.

Clinical characteristics of natalizumab-associated PML

Several clinical observations should increase suspicion of natalizumab-associated PML.^3–5 For example, the most common presenting symptoms are cognitive, motor, language, and visual impairment. Gadolinium-enhancing lesions are observed at presentation in about one-half of patients. Seizures and paroxysmal events can occur at presentation, which helps to differentiate PML from an MS relapse.

Approximately one-half of patients with natalizumab-associated PML have an initial viral load of less than 500 copies/mL, underscoring the need for ultrasensitive polymerase chain reaction (PCR) testing. An ultrasensitive JCV assay (Focus Diagnostics, Cypress, California) is available that can detect less than 50 copies/mL of JCV DNA. Because the viral copy numbers in the cerebrospinal fluid (CSF) may be low in patients treated with natalizumab, the CSF PCR may be falsely negative. In several cases of PML, JCV was undetectable in the CSF by PCR, identified only later by repeat PCR or brain biopsy.⁴ Serum JCV PCR is not useful in the screening or diagnosis of PML.

Natalizumab-associated PML has not been observed with therapy of 6 months’ or less duration. After 6 months of natalizumab therapy, new MRI lesions are rare in patients who are negative for neutralizing antibodies. A new MRI lesion in such a patient should be considered suspicious for PML. Our standard protocol is to check for neutralizing antibodies at 6 months in all patients treated with natalizumab. Symptoms of PML develop in affected patients whose duration of therapy ranges from 6 to 81 infusions. Symptoms often develop well before PML is diagnosed.^4,5

Forty-six percent of patients treated with natalizumab who develop PML have received previous autologous bone marrow transplantation or chemo therapy, including mitoxantrone, azathioprine, methotrexate, and mycophenolate mofetil. In comparison, up to 25% of MS patients who were treated with natalizumab (13% in the United States, 24% in Europe) have had prior chemotherapy treatment. Prior immunosuppressive therapy increases the risk of PML by two- to fourfold, which may explain the higher rate of PML in Europe compared with that of the United States.^4,5

Testing for immune response to JCV

A JCV enzyme-linked immunosorbent assay (ELISA) test has been developed that identifies patients with an immune response to JCV. Among MS patients, 55% test positive for JCV through this assay.⁶ The false-negative rate of the test is 5%, and the overall annual seroconversion rate is estimated to be about 2%, necessitating repeat testing.

Based on results of this assay, the estimated risk of PML in seropositive patients is about 1 in 500.⁶ The test was positive in 28 of 28 patients who developed PML. The probability of this relationship occurring by chance is 0.5528, which suggests that this assay is useful to stratify risk for development of PML. Although the rate of false negatives makes the test an imperfect predictor, it is still useful in clinical practice. The test became available clinically in late summer 2011. Further longitudinal observation studies (STRATIFY-1 and STRATIFY-2) on the use of the JCV ELISA to detect anti-JCV antibodies in the blood of natalizumab-treated patients with MS are under way.

Stratifying risk for natalizumab-related PML

The possibility of reducing the risk of PML in natalizumab-treated patients through natalizumab holidays is attractive. When exploring this option, one must consider whether the risk of recurrent disease activity with treatment interruption outweighs the potentially decreased risk of PML.⁸ A randomized controlled multicenter clinical trial of natalizumab interruption is ongoing, with the recruitment phase complete after enrollment of 175 patients. Patients taking natalizumab at study entry have been randomized to one of three arms: continuation of monthly natalizumab for 6 months, placebo for 6 months, or an alternate treatment (interferon beta-1a, glatiramer acetate, or monthly intravenous steroids) for 6 months administered open-label by clinician and patient choice.

The primary outcome measures are markers of immune function and overall disease activity during treatment interruption and after resumption. Patients are monitored monthly using MRI to measure disease activity. Those who experience relapse will have the option of returning to natalizumab therapy or switching to an alternate treatment. The results of this prospective, randomized, controlled trial will provide a greater understanding of the safety issues surrounding natalizumab holidays.

Management of natalizumab-related PML

Management of patients taking natalizumab starts with risk stratification in an attempt to prevent the development of PML. If suspicion for PML is raised based on symptoms, early diagnosis can be accomplished through the use of a sensitive JCV PCR assay, with a repeat PCR if negative. Natalizumab treatment should be withheld during the workup for PML.

Reprinted, with permission, from Neurology (Khatri BO, et al. Effect of plasma exchange in accelerating natalizumab clearance and restoring leukocyte function. Neurology 2009; 72:402–409).

When immunosuppression is rapidly reversed in cases of natalizumab-associated PML, an overly exuberant immune response targeting JCV in the CNS is observed 2 to 6 weeks later. The response, termed immune reconstitution inflammatory syndrome (IRIS), is not always easy to differentiate from progression of PML. Nonetheless, most clinicians recommend high-dose corticosteroids if a clinical and imaging syndrome resembling IRIS develops several weeks after immune restoration.¹⁰ The objective is to achieve the immune reconstitution needed to control JCV infection while limiting the collateral damage of inflammation on the remaining brain tissue.

SUMMARY

Risk factors for natalizumab-associated PML include duration of treatment with natalizumab, previous chemotherapy, and JCV antibody serology. Early diagnosis requires the use of an ultrasensitive JCV PCR assay. Treatment is focused on early diagnosis, immediate cessation of pharmacologic causes of immunosuppression, and active efforts to accelerate immune restoration.

DISCUSSION

Dr. Calabrese: What are your thoughts about plasmapheresis for rituximab-related cases of PML?

Dr. Fox: It’s probably not going to be as helpful as with natalizumab. Rituximab has pharmacokinetics that are similar to those of other monoclonal antibodies, with a half-life in the range of 14 to 20 days. So it’s pretty much absent from the body within 1 to 2 months of infusion. The enduring benefit from rituximab comes not from the persistent presence of the monoclonal antibody, but the persistent absence of CD19 B cells. Plasmapheresis is unlikely to be effective because it won’t accelerate return of CD19 B cells to the peripheral circulation. In rituximab-related PML, stimulating the bone marrow to produce more B cells in order to restore the immune system is more likely to be effective. In contrast, I did recommend plasma pheresis in a case of efalizumab-related PML. Because efalizumab is a binding antibody to the CD11a receptor, we wanted to accelerate its removal.

Dr. Molloy: In an MS patient who responds well to natalizumab, do you ever explore a strategy of dose reduction or extending the dosing interval of natalizumab?

Dr. Fox: Let me put that into a clinical context. A 35-year old man has had relapsing-remitting MS for 3 years. Two years ago, after disease activity occurred while he was using an injectable therapy, he started natalizumab and has been clinically and radiologically stable on natalizumab. Then, he gets the JCV assay, it’s positive, and he asks if it’s time to get off natalizumab “because of the risk of that brain virus.”

What do I tell him? Should I change the dosing interval? At this point, we are not doing either. One reason is the unpredictable pharmacokinetics of the drug. The dose and dosing regimen were chosen to have 85% or greater receptor saturation in 95% or more of patients over the course of the recommended 4-week dosing interval. If you increase the interval to 6 weeks or 8 weeks, you can’t predict in individual patients whether or not meaningful desaturation occurs and thus allows some immune cells to enter the brain to protect against PML (but not too many, or MS disease activity will return).

Dr. Simpson: Do you have an algorithm for working up patients?

Dr. Fox: It depends on the level of suspicion given the patient’s symptoms. It’s difficult to find a single MS patient who does not have some fluctuation of symptoms over time and some worsening of symptoms such as stiffness, fatigue, and cognitive difficulties. They all have changes in mood, so if one took any symptom change—any change in their report of mood and cognition— as the cutoff for a workup, we wouldn’t be giving natalizumab at all. But if a patient or family says, “I am worried,” then we need to work it up. Also, if there are clearcut new or worsening neurologic symptoms, we pursue a workup. Often, the change in symptoms is revealed when the patient comes in for his or her monthly infusion and the nurse asks the four questions from the preinfusion checklist (as part of the mandatory Tysabri Outreach: Unified Commitment to Health [TOUCH] prescribing program for natalizumab).¹¹

If there are new symptoms, we hold infusions and do a two-stage evaluation. The first stage is a brain MRI to evaluate for change from baseline (the US Food and Drug Administration requires a brain MRI at baseline before starting natalizumab therapy). Most patients undergo a brain MRI every 6 to 12 months while on natalizumab therapy, with instructions to the neuroradiologist to evaluate carefully for new lesions. In our institution, the PML MRI evaluation is a fine-toothcomb assessment of lesions from the most recent MRI compared with the current MRI. Depending on the results of the current MRI and on our level of suspicion, we may proceed to a spinal tap, even if the MRI findings are stable. We have done 8 to 10 spinal taps in patients taking natalizumab when we were suspicious enough to evaluate for PML. Occasional patients continue to have active disease, relapses, and new lesions even without developing antibodies while taking natalizumab.

Dr. Rudick: We need a quick, quantitative analysis method to compare one MRI with another. It is easy to say, “Consider PML if there are new lesions.” It’s not so easy to know if the lesions are new. We are participating in a National Institutes of Health study regarding identification of biomarkers of interferon’s effects, and the study requires obtaining MRI scans at baseline and 6 months. We have state-of-the-art subtraction MRI to quantify new lesions on the followup MRI. However, there is significant disagreement on the number of new lesions determined by clinical raters, and disagreement between the clinical raters and the numbers generated by the computer program.

Dr. Major: Is the incidence of natalizumab-related PML based on the number of months or on the number of infusions?

Dr. Fox: It is based on the number of infusions. You bring up a good point because these patients may interrupt treatment when they go on vacation, for example, or have a lapse in insurance coverage. Most patients follow the every-4-weeks protocol and receive 13 infusions in a year. Perhaps 10% to 15% do not follow it precisely.

Dr. Molloy: Is everyone who takes natalizumab being followed for PML even if they discontinue natalizumab? Have any differences emerged in the factors that predispose to PML among those who continue therapy compared with those who discontinue? I ask because I’m wondering why the incidence appears to stabilize, or even go down, after 36 infusions.

Dr. Fox: PML has not been reported beyond several months after stopping natalizumab; concern about PML can decrease fairly quickly after stopping the drug. Many of us expected the risk of PML to continue rising with cumulative treatment, so were pleasantly surprised to see a plateau in the risk of PML after about 36 months. We don’t understand what leads to this plateau.

Progressive multifocal leukoencephalopathy (PML) is a rare opportunistic infection of the central nervous system (CNS). Although originally associated with broad-based immunosuppression (human immunodeficiency virus infection, lymphoproliferative disorders, and immunosuppressive medications), recognition of PML in patients with selective immunosuppression is growing. This restricted immunodeviation can arise from autoimmune disorders such as systemic lupus erythematosus, selective immunosuppressive therapies (eg, rituximab, leflunomide, and efalizumab), or immunosuppression limited to the CNS (eg, treatment with natalizumab).

This article reviews approaches to the management of PML, with specific recommendations regarding PML associated with natalizumab therapy.

APPROACH TO PML TREATMENT

The ideal approach to PML treatment is generally two-pronged: antiviral therapies to directly reduce viral replication and immune reconstitution that empowers the immune system to attack the JC virus (JCV). Challenges to treatment are the difficulty in culturing JCV for in vitro studies, lack of an animal model of PML, and infrequency of PML cases.

Antiviral therapies

At present, no antiviral agent has confirmed efficacy in PML. Nucleoside analogues, serotonin 5-hydroxytryptamine receptor antagonists (to block the JCV receptor), and several cytokines provided exciting prospects in preclinical studies for treatment of PML in humans. Unfortunately, subsequent clinical studies of cytarabine, cidofovir, and interferon alfa all yielded disappointing results. A derivative of cidofovir, CMX001, is also being evaluated for efficacy in PML. Mefloquine was identified through a broad pharmaceutical screening study to have strong antiviral effects in vitro, but a clinical trial to assess its effects was stopped. It remains unclear whether the failure of clinical studies after successful in vitro studies is secondary to low drug penetration into the CNS, treatment initiation too late in the course of PML, or other differences not yet fully understood.

Immune reconstitution

Given the widespread failure of antiviral regimens, the mainstay of PML treatment is immune reconstitution. When immunosuppression is secondary to a medical disorder, efforts are pursued to reverse the primary disorder. For example, highly active antiretroviral therapy significantly prolongs survival in antiretroviral-naïve acquired immunodeficiency syndrome patients.^1,2 Decreasing the intensity of immunosuppressive therapy in solid organ transplant may improve survival with PML. When PML is associated with biologic therapies for autoimmune diseases, early diagnosis and immediate suspension of therapy is thought to improve outcomes.

EXPERIENCE WITH NATALIZUMAB

PML in the setting of natalizumab therapy is related to cumulative exposure to natalizumab. As of August 4, 2011, there had been 150 cases of natalizumab-related PML documented in more than 88,000 patients exposed to natalizumab worldwide³ (see page S18, “Multiple sclerosis, natalizumab, and PML: Helping patients decide”). The incidence of PML in natalizumab-treated patients varies according to the number of infusions received, but the incidence of PML by each epoch of treatment exposure (1 to 24 infusions, 25 to 36 infusions, 37 to 48 infusions) appears to have remained stable over time.³

The mortality associated with natalizumab-related PML was 19% (29 deaths among the 150 confirmed cases) as of August 4, 2011.³ In cases with at least 6 months of follow-up, mortality has remained at about 20%. Many who survived were left with serious morbidity and permanent disability, although interpretation of disability is difficult because functional impairment is a hallmark of multiple sclerosis (MS) irrespective of PML. Survival in patients with natalizumab-associated PML appears to be better than with PML associated with other conditions, possibly because of early diagnosis achieved through clinical vigilance and swift immune reconstitution through natalizumab discontinuation and either plasmapheresis or immunoabsorption. Predictors of survival include younger age at diagnosis, less disability prior to onset of PML, more localized disease on magnetic resonance imaging (MRI) of the brain, and shorter time from symptom onset to PML diagnosis.

Clinical characteristics of natalizumab-associated PML

Several clinical observations should increase suspicion of natalizumab-associated PML.^3–5 For example, the most common presenting symptoms are cognitive, motor, language, and visual impairment. Gadolinium-enhancing lesions are observed at presentation in about one-half of patients. Seizures and paroxysmal events can occur at presentation, which helps to differentiate PML from an MS relapse.

Approximately one-half of patients with natalizumab-associated PML have an initial viral load of less than 500 copies/mL, underscoring the need for ultrasensitive polymerase chain reaction (PCR) testing. An ultrasensitive JCV assay (Focus Diagnostics, Cypress, California) is available that can detect less than 50 copies/mL of JCV DNA. Because the viral copy numbers in the cerebrospinal fluid (CSF) may be low in patients treated with natalizumab, the CSF PCR may be falsely negative. In several cases of PML, JCV was undetectable in the CSF by PCR, identified only later by repeat PCR or brain biopsy.⁴ Serum JCV PCR is not useful in the screening or diagnosis of PML.

Natalizumab-associated PML has not been observed with therapy of 6 months’ or less duration. After 6 months of natalizumab therapy, new MRI lesions are rare in patients who are negative for neutralizing antibodies. A new MRI lesion in such a patient should be considered suspicious for PML. Our standard protocol is to check for neutralizing antibodies at 6 months in all patients treated with natalizumab. Symptoms of PML develop in affected patients whose duration of therapy ranges from 6 to 81 infusions. Symptoms often develop well before PML is diagnosed.^4,5

Forty-six percent of patients treated with natalizumab who develop PML have received previous autologous bone marrow transplantation or chemo therapy, including mitoxantrone, azathioprine, methotrexate, and mycophenolate mofetil. In comparison, up to 25% of MS patients who were treated with natalizumab (13% in the United States, 24% in Europe) have had prior chemotherapy treatment. Prior immunosuppressive therapy increases the risk of PML by two- to fourfold, which may explain the higher rate of PML in Europe compared with that of the United States.^4,5

Testing for immune response to JCV

A JCV enzyme-linked immunosorbent assay (ELISA) test has been developed that identifies patients with an immune response to JCV. Among MS patients, 55% test positive for JCV through this assay.⁶ The false-negative rate of the test is 5%, and the overall annual seroconversion rate is estimated to be about 2%, necessitating repeat testing.

Based on results of this assay, the estimated risk of PML in seropositive patients is about 1 in 500.⁶ The test was positive in 28 of 28 patients who developed PML. The probability of this relationship occurring by chance is 0.5528, which suggests that this assay is useful to stratify risk for development of PML. Although the rate of false negatives makes the test an imperfect predictor, it is still useful in clinical practice. The test became available clinically in late summer 2011. Further longitudinal observation studies (STRATIFY-1 and STRATIFY-2) on the use of the JCV ELISA to detect anti-JCV antibodies in the blood of natalizumab-treated patients with MS are under way.

Stratifying risk for natalizumab-related PML

The possibility of reducing the risk of PML in natalizumab-treated patients through natalizumab holidays is attractive. When exploring this option, one must consider whether the risk of recurrent disease activity with treatment interruption outweighs the potentially decreased risk of PML.⁸ A randomized controlled multicenter clinical trial of natalizumab interruption is ongoing, with the recruitment phase complete after enrollment of 175 patients. Patients taking natalizumab at study entry have been randomized to one of three arms: continuation of monthly natalizumab for 6 months, placebo for 6 months, or an alternate treatment (interferon beta-1a, glatiramer acetate, or monthly intravenous steroids) for 6 months administered open-label by clinician and patient choice.

The primary outcome measures are markers of immune function and overall disease activity during treatment interruption and after resumption. Patients are monitored monthly using MRI to measure disease activity. Those who experience relapse will have the option of returning to natalizumab therapy or switching to an alternate treatment. The results of this prospective, randomized, controlled trial will provide a greater understanding of the safety issues surrounding natalizumab holidays.

Management of natalizumab-related PML

Management of patients taking natalizumab starts with risk stratification in an attempt to prevent the development of PML. If suspicion for PML is raised based on symptoms, early diagnosis can be accomplished through the use of a sensitive JCV PCR assay, with a repeat PCR if negative. Natalizumab treatment should be withheld during the workup for PML.

Reprinted, with permission, from Neurology (Khatri BO, et al. Effect of plasma exchange in accelerating natalizumab clearance and restoring leukocyte function. Neurology 2009; 72:402–409).

When immunosuppression is rapidly reversed in cases of natalizumab-associated PML, an overly exuberant immune response targeting JCV in the CNS is observed 2 to 6 weeks later. The response, termed immune reconstitution inflammatory syndrome (IRIS), is not always easy to differentiate from progression of PML. Nonetheless, most clinicians recommend high-dose corticosteroids if a clinical and imaging syndrome resembling IRIS develops several weeks after immune restoration.¹⁰ The objective is to achieve the immune reconstitution needed to control JCV infection while limiting the collateral damage of inflammation on the remaining brain tissue.

SUMMARY

Risk factors for natalizumab-associated PML include duration of treatment with natalizumab, previous chemotherapy, and JCV antibody serology. Early diagnosis requires the use of an ultrasensitive JCV PCR assay. Treatment is focused on early diagnosis, immediate cessation of pharmacologic causes of immunosuppression, and active efforts to accelerate immune restoration.

DISCUSSION

Dr. Calabrese: What are your thoughts about plasmapheresis for rituximab-related cases of PML?

Dr. Fox: It’s probably not going to be as helpful as with natalizumab. Rituximab has pharmacokinetics that are similar to those of other monoclonal antibodies, with a half-life in the range of 14 to 20 days. So it’s pretty much absent from the body within 1 to 2 months of infusion. The enduring benefit from rituximab comes not from the persistent presence of the monoclonal antibody, but the persistent absence of CD19 B cells. Plasmapheresis is unlikely to be effective because it won’t accelerate return of CD19 B cells to the peripheral circulation. In rituximab-related PML, stimulating the bone marrow to produce more B cells in order to restore the immune system is more likely to be effective. In contrast, I did recommend plasma pheresis in a case of efalizumab-related PML. Because efalizumab is a binding antibody to the CD11a receptor, we wanted to accelerate its removal.

Dr. Molloy: In an MS patient who responds well to natalizumab, do you ever explore a strategy of dose reduction or extending the dosing interval of natalizumab?

Dr. Fox: Let me put that into a clinical context. A 35-year old man has had relapsing-remitting MS for 3 years. Two years ago, after disease activity occurred while he was using an injectable therapy, he started natalizumab and has been clinically and radiologically stable on natalizumab. Then, he gets the JCV assay, it’s positive, and he asks if it’s time to get off natalizumab “because of the risk of that brain virus.”

What do I tell him? Should I change the dosing interval? At this point, we are not doing either. One reason is the unpredictable pharmacokinetics of the drug. The dose and dosing regimen were chosen to have 85% or greater receptor saturation in 95% or more of patients over the course of the recommended 4-week dosing interval. If you increase the interval to 6 weeks or 8 weeks, you can’t predict in individual patients whether or not meaningful desaturation occurs and thus allows some immune cells to enter the brain to protect against PML (but not too many, or MS disease activity will return).

Dr. Simpson: Do you have an algorithm for working up patients?

Dr. Fox: It depends on the level of suspicion given the patient’s symptoms. It’s difficult to find a single MS patient who does not have some fluctuation of symptoms over time and some worsening of symptoms such as stiffness, fatigue, and cognitive difficulties. They all have changes in mood, so if one took any symptom change—any change in their report of mood and cognition— as the cutoff for a workup, we wouldn’t be giving natalizumab at all. But if a patient or family says, “I am worried,” then we need to work it up. Also, if there are clearcut new or worsening neurologic symptoms, we pursue a workup. Often, the change in symptoms is revealed when the patient comes in for his or her monthly infusion and the nurse asks the four questions from the preinfusion checklist (as part of the mandatory Tysabri Outreach: Unified Commitment to Health [TOUCH] prescribing program for natalizumab).¹¹

If there are new symptoms, we hold infusions and do a two-stage evaluation. The first stage is a brain MRI to evaluate for change from baseline (the US Food and Drug Administration requires a brain MRI at baseline before starting natalizumab therapy). Most patients undergo a brain MRI every 6 to 12 months while on natalizumab therapy, with instructions to the neuroradiologist to evaluate carefully for new lesions. In our institution, the PML MRI evaluation is a fine-toothcomb assessment of lesions from the most recent MRI compared with the current MRI. Depending on the results of the current MRI and on our level of suspicion, we may proceed to a spinal tap, even if the MRI findings are stable. We have done 8 to 10 spinal taps in patients taking natalizumab when we were suspicious enough to evaluate for PML. Occasional patients continue to have active disease, relapses, and new lesions even without developing antibodies while taking natalizumab.

Dr. Rudick: We need a quick, quantitative analysis method to compare one MRI with another. It is easy to say, “Consider PML if there are new lesions.” It’s not so easy to know if the lesions are new. We are participating in a National Institutes of Health study regarding identification of biomarkers of interferon’s effects, and the study requires obtaining MRI scans at baseline and 6 months. We have state-of-the-art subtraction MRI to quantify new lesions on the followup MRI. However, there is significant disagreement on the number of new lesions determined by clinical raters, and disagreement between the clinical raters and the numbers generated by the computer program.

Dr. Major: Is the incidence of natalizumab-related PML based on the number of months or on the number of infusions?

Dr. Fox: It is based on the number of infusions. You bring up a good point because these patients may interrupt treatment when they go on vacation, for example, or have a lapse in insurance coverage. Most patients follow the every-4-weeks protocol and receive 13 infusions in a year. Perhaps 10% to 15% do not follow it precisely.

Dr. Molloy: Is everyone who takes natalizumab being followed for PML even if they discontinue natalizumab? Have any differences emerged in the factors that predispose to PML among those who continue therapy compared with those who discontinue? I ask because I’m wondering why the incidence appears to stabilize, or even go down, after 36 infusions.

Dr. Fox: PML has not been reported beyond several months after stopping natalizumab; concern about PML can decrease fairly quickly after stopping the drug. Many of us expected the risk of PML to continue rising with cumulative treatment, so were pleasantly surprised to see a plateau in the risk of PML after about 36 months. We don’t understand what leads to this plateau.

To the Editor: I read with interest the article by Drs. Callahan and Baranowski¹ in your April 2011 issue about managing newly diagnosed atrial fibrillation. I believe several issues merit further discussion.

First of all, as mentioned in the article, pulmonary vein isolation, or radiofrequency catheter ablation of the left atrium, can cure paroxysmal atrial fibrillation. Callahan and Baranowski described the optimal indication for this procedure, but they failed to mention the potential adverse effects, that is, esophageal ulcer and atrio-esophageal fistula.² Owing to the proximity of the esophagus and the accompanying vagus nerve to the posterior wall of the left atrium, it is estimated that 47% of patients develop thermal mucosal injury and 18% develop esophageal ulcer after ablation, while 0.5% develop atrio-esophageal fistula.³ Gastric hypomotility and pyloric spasm are reported as well. It would therefore be prudent to inform patients of such risks if a persistently symptomatic young patient demands this procedure, since the damage might be long-lasting.

In addition, in deciding on long-term anticoagulation for patients with atrial fibrillation, the CHADS₂ score is often utilized (1 point each for congestive heart failure, hypertension, age 75 or older, and diabetes mellitus; 2 points for prior stroke or transient ischemic attack). Although it is validated and widely applicable, the CHADS₂ score carries the disadvantages of oversimplification and of overclassifying atrial fibrillation patients into the intermediate-risk category.⁴ Lip et al,⁵ in a seminal article surveying a large group of patients who had nonvalvular atrial fibrillation, proposed using a new and also simple risk stratification scheme, the 2009 Birmingham scheme. This scheme uses the acronym CHA₂DS₂-VASc and differs from the CHADS₂ score in that patients age 75 or older get 2 points, those age 65 to 74 get 1 point, those with vascular disease get 1 point, and women get 1 point. They show that this new scheme fares marginally better than the original CHADS₂ score, with fewer patients wrongly assigned to the intermediate-risk category. That means a lower percentage of patients will receive unnecessary anticoagulation and suffer from unneeded anguish. Subsequent studies also prove that this newer scoring index possesses higher sensitivity and predicts thromboembolic events more accurately than the CHADS₂ score. Thus, I believe this should also be factored into the decision process when initiating warfarin in atrial fibrillation patients, especially in light of the fact that scanty evidence exists for the use of newer anticoagulants based on the CHADS₂ score.

To the Editor: I read with interest the article by Drs. Callahan and Baranowski¹ in your April 2011 issue about managing newly diagnosed atrial fibrillation. I believe several issues merit further discussion.

First of all, as mentioned in the article, pulmonary vein isolation, or radiofrequency catheter ablation of the left atrium, can cure paroxysmal atrial fibrillation. Callahan and Baranowski described the optimal indication for this procedure, but they failed to mention the potential adverse effects, that is, esophageal ulcer and atrio-esophageal fistula.² Owing to the proximity of the esophagus and the accompanying vagus nerve to the posterior wall of the left atrium, it is estimated that 47% of patients develop thermal mucosal injury and 18% develop esophageal ulcer after ablation, while 0.5% develop atrio-esophageal fistula.³ Gastric hypomotility and pyloric spasm are reported as well. It would therefore be prudent to inform patients of such risks if a persistently symptomatic young patient demands this procedure, since the damage might be long-lasting.

In addition, in deciding on long-term anticoagulation for patients with atrial fibrillation, the CHADS₂ score is often utilized (1 point each for congestive heart failure, hypertension, age 75 or older, and diabetes mellitus; 2 points for prior stroke or transient ischemic attack). Although it is validated and widely applicable, the CHADS₂ score carries the disadvantages of oversimplification and of overclassifying atrial fibrillation patients into the intermediate-risk category.⁴ Lip et al,⁵ in a seminal article surveying a large group of patients who had nonvalvular atrial fibrillation, proposed using a new and also simple risk stratification scheme, the 2009 Birmingham scheme. This scheme uses the acronym CHA₂DS₂-VASc and differs from the CHADS₂ score in that patients age 75 or older get 2 points, those age 65 to 74 get 1 point, those with vascular disease get 1 point, and women get 1 point. They show that this new scheme fares marginally better than the original CHADS₂ score, with fewer patients wrongly assigned to the intermediate-risk category. That means a lower percentage of patients will receive unnecessary anticoagulation and suffer from unneeded anguish. Subsequent studies also prove that this newer scoring index possesses higher sensitivity and predicts thromboembolic events more accurately than the CHADS₂ score. Thus, I believe this should also be factored into the decision process when initiating warfarin in atrial fibrillation patients, especially in light of the fact that scanty evidence exists for the use of newer anticoagulants based on the CHADS₂ score.

To the Editor: I read with interest the article by Drs. Callahan and Baranowski¹ in your April 2011 issue about managing newly diagnosed atrial fibrillation. I believe several issues merit further discussion.

First of all, as mentioned in the article, pulmonary vein isolation, or radiofrequency catheter ablation of the left atrium, can cure paroxysmal atrial fibrillation. Callahan and Baranowski described the optimal indication for this procedure, but they failed to mention the potential adverse effects, that is, esophageal ulcer and atrio-esophageal fistula.² Owing to the proximity of the esophagus and the accompanying vagus nerve to the posterior wall of the left atrium, it is estimated that 47% of patients develop thermal mucosal injury and 18% develop esophageal ulcer after ablation, while 0.5% develop atrio-esophageal fistula.³ Gastric hypomotility and pyloric spasm are reported as well. It would therefore be prudent to inform patients of such risks if a persistently symptomatic young patient demands this procedure, since the damage might be long-lasting.

In addition, in deciding on long-term anticoagulation for patients with atrial fibrillation, the CHADS₂ score is often utilized (1 point each for congestive heart failure, hypertension, age 75 or older, and diabetes mellitus; 2 points for prior stroke or transient ischemic attack). Although it is validated and widely applicable, the CHADS₂ score carries the disadvantages of oversimplification and of overclassifying atrial fibrillation patients into the intermediate-risk category.⁴ Lip et al,⁵ in a seminal article surveying a large group of patients who had nonvalvular atrial fibrillation, proposed using a new and also simple risk stratification scheme, the 2009 Birmingham scheme. This scheme uses the acronym CHA₂DS₂-VASc and differs from the CHADS₂ score in that patients age 75 or older get 2 points, those age 65 to 74 get 1 point, those with vascular disease get 1 point, and women get 1 point. They show that this new scheme fares marginally better than the original CHADS₂ score, with fewer patients wrongly assigned to the intermediate-risk category. That means a lower percentage of patients will receive unnecessary anticoagulation and suffer from unneeded anguish. Subsequent studies also prove that this newer scoring index possesses higher sensitivity and predicts thromboembolic events more accurately than the CHADS₂ score. Thus, I believe this should also be factored into the decision process when initiating warfarin in atrial fibrillation patients, especially in light of the fact that scanty evidence exists for the use of newer anticoagulants based on the CHADS₂ score.

In Reply: Dr. Chao raises several important points regarding our manuscript on the management of newly diagnosed atrial fibrillation.¹

Dr. Chao mentions some of the complications of pulmonary vein antrum isolation. A review of catheter ablation for atrial fibrillation was outside the scope of our manuscript, so the details of the procedure and potential complications were not covered. Dr. Chao does mention some of the important potential complications. However, the complication rates he cites are not generally supported by the available medical literature. Thermal mucosal injury of the esophagus was reported at rates as low as 4% in the same studies cited by Dr. Chao in patients undergoing pulmonary vein antrum isolation with conscious sedation. The rate of 47% was seen in patients undergoing the procedure with general anesthesia. The rate of atrio-esophageal fistula is not well known. As of 2010, about 49 cases were reported in the literature.² Rates have been described ranging from 0.01% to 0.2%,^3–9 far lower than the rate mentioned by Dr. Chao. A careful review with the patient of the risks, benefits, and alternatives is standard practice before any elective, invasive procedure.

Multiple anticoagulation schemes have been proposed, including the Birmingham 2009 scheme.¹⁰ We included the CHADS₂ score in our paper because it is widely accepted and well validated. The Birmingham 2009 scheme acknowledges other potential risk factors such as female sex, history of vascular disease, and age between 65 and 75 years. It will be interesting to see if it will ever supplant the CHADS₂ score. However, no risk stratification scheme should replace sound clinical judgment. Individual patient factors must be considered when deciding whether anticoagulation is appropriate for an individual patient.

In Reply: Dr. Chao raises several important points regarding our manuscript on the management of newly diagnosed atrial fibrillation.¹

Dr. Chao mentions some of the complications of pulmonary vein antrum isolation. A review of catheter ablation for atrial fibrillation was outside the scope of our manuscript, so the details of the procedure and potential complications were not covered. Dr. Chao does mention some of the important potential complications. However, the complication rates he cites are not generally supported by the available medical literature. Thermal mucosal injury of the esophagus was reported at rates as low as 4% in the same studies cited by Dr. Chao in patients undergoing pulmonary vein antrum isolation with conscious sedation. The rate of 47% was seen in patients undergoing the procedure with general anesthesia. The rate of atrio-esophageal fistula is not well known. As of 2010, about 49 cases were reported in the literature.² Rates have been described ranging from 0.01% to 0.2%,^3–9 far lower than the rate mentioned by Dr. Chao. A careful review with the patient of the risks, benefits, and alternatives is standard practice before any elective, invasive procedure.

Multiple anticoagulation schemes have been proposed, including the Birmingham 2009 scheme.¹⁰ We included the CHADS₂ score in our paper because it is widely accepted and well validated. The Birmingham 2009 scheme acknowledges other potential risk factors such as female sex, history of vascular disease, and age between 65 and 75 years. It will be interesting to see if it will ever supplant the CHADS₂ score. However, no risk stratification scheme should replace sound clinical judgment. Individual patient factors must be considered when deciding whether anticoagulation is appropriate for an individual patient.

In Reply: Dr. Chao raises several important points regarding our manuscript on the management of newly diagnosed atrial fibrillation.¹

Dr. Chao mentions some of the complications of pulmonary vein antrum isolation. A review of catheter ablation for atrial fibrillation was outside the scope of our manuscript, so the details of the procedure and potential complications were not covered. Dr. Chao does mention some of the important potential complications. However, the complication rates he cites are not generally supported by the available medical literature. Thermal mucosal injury of the esophagus was reported at rates as low as 4% in the same studies cited by Dr. Chao in patients undergoing pulmonary vein antrum isolation with conscious sedation. The rate of 47% was seen in patients undergoing the procedure with general anesthesia. The rate of atrio-esophageal fistula is not well known. As of 2010, about 49 cases were reported in the literature.² Rates have been described ranging from 0.01% to 0.2%,^3–9 far lower than the rate mentioned by Dr. Chao. A careful review with the patient of the risks, benefits, and alternatives is standard practice before any elective, invasive procedure.

Multiple anticoagulation schemes have been proposed, including the Birmingham 2009 scheme.¹⁰ We included the CHADS₂ score in our paper because it is widely accepted and well validated. The Birmingham 2009 scheme acknowledges other potential risk factors such as female sex, history of vascular disease, and age between 65 and 75 years. It will be interesting to see if it will ever supplant the CHADS₂ score. However, no risk stratification scheme should replace sound clinical judgment. Individual patient factors must be considered when deciding whether anticoagulation is appropriate for an individual patient.

To the Editor: The interesting report by Korniyenko and colleagues of the delayed diagnosis of visceral angioedema due to angiotensin-converting enzyme (ACE) inhibitor therapy¹ should alert readers that a long duration of use of ACE inhibitors should not rule out the diagnosis of ACE inhibitor-induced angioedema, as symptoms can be delayed for up to a decade.

Risk factors for angioedema for patients on ACE inhibitor therapy that have been identified so far include black race, the XPNPEP2 C-2399A polymorphism in men (which leads to decreased aminopeptidase P activity),² and concomitant use of the mTOR inhibitors sirolimus (Rapamune) or everolimus (Afinitor) in renal transplant recipients.³ All of these factors further decrease metabolism of the vasoactive peptide bradykinin. However, the effect of cofactors such as use of nonsteroidal anti-inflammatory drugs, aspirin, simvastatin, estrogen, or a tendency for angioedema (such as in patients with recurrent or episodic idiopathic angioedema) on lowering the threshold for angioedema or increasing the severity of the angioedema episode or episodes after starting ACE inhibitor therapy remains unknown.

Physicians should also be aware of angioedema as a significant side effect of the new renin inhibitor aliskiren (marketed by Novartis Pharmaceuticals as Rasilez in the United Kingdom and as Tekturna in the United States) for treatment of essential hypertension.⁴ A pooled analysis of 31 studies in 12,188 patients showed the incidence of angioedema associated with aliskiren monotherapy to be 0.4%, similar to that with ACE inhibitors: relative risk 0.31, 95% confidence interval 0.07–1.47 for 150 mg; relative risk 0.57, 95% confidence interval 0.17–1.89 for 300 mg).⁵ However, no patients were hospitalized with a serious angioedema event.

Although the mechanism of action of aliskiren via renin inhibition would suggest that bradykinin may not be the causative agent of angioedema, physicians should ensure that patients who report significant angioedema episodes or those who present with angioedema have their medication history thoroughly reviewed to prevent a serious untoward event.

To the Editor: The interesting report by Korniyenko and colleagues of the delayed diagnosis of visceral angioedema due to angiotensin-converting enzyme (ACE) inhibitor therapy¹ should alert readers that a long duration of use of ACE inhibitors should not rule out the diagnosis of ACE inhibitor-induced angioedema, as symptoms can be delayed for up to a decade.

Risk factors for angioedema for patients on ACE inhibitor therapy that have been identified so far include black race, the XPNPEP2 C-2399A polymorphism in men (which leads to decreased aminopeptidase P activity),² and concomitant use of the mTOR inhibitors sirolimus (Rapamune) or everolimus (Afinitor) in renal transplant recipients.³ All of these factors further decrease metabolism of the vasoactive peptide bradykinin. However, the effect of cofactors such as use of nonsteroidal anti-inflammatory drugs, aspirin, simvastatin, estrogen, or a tendency for angioedema (such as in patients with recurrent or episodic idiopathic angioedema) on lowering the threshold for angioedema or increasing the severity of the angioedema episode or episodes after starting ACE inhibitor therapy remains unknown.

Physicians should also be aware of angioedema as a significant side effect of the new renin inhibitor aliskiren (marketed by Novartis Pharmaceuticals as Rasilez in the United Kingdom and as Tekturna in the United States) for treatment of essential hypertension.⁴ A pooled analysis of 31 studies in 12,188 patients showed the incidence of angioedema associated with aliskiren monotherapy to be 0.4%, similar to that with ACE inhibitors: relative risk 0.31, 95% confidence interval 0.07–1.47 for 150 mg; relative risk 0.57, 95% confidence interval 0.17–1.89 for 300 mg).⁵ However, no patients were hospitalized with a serious angioedema event.

Although the mechanism of action of aliskiren via renin inhibition would suggest that bradykinin may not be the causative agent of angioedema, physicians should ensure that patients who report significant angioedema episodes or those who present with angioedema have their medication history thoroughly reviewed to prevent a serious untoward event.

To the Editor: The interesting report by Korniyenko and colleagues of the delayed diagnosis of visceral angioedema due to angiotensin-converting enzyme (ACE) inhibitor therapy¹ should alert readers that a long duration of use of ACE inhibitors should not rule out the diagnosis of ACE inhibitor-induced angioedema, as symptoms can be delayed for up to a decade.

Risk factors for angioedema for patients on ACE inhibitor therapy that have been identified so far include black race, the XPNPEP2 C-2399A polymorphism in men (which leads to decreased aminopeptidase P activity),² and concomitant use of the mTOR inhibitors sirolimus (Rapamune) or everolimus (Afinitor) in renal transplant recipients.³ All of these factors further decrease metabolism of the vasoactive peptide bradykinin. However, the effect of cofactors such as use of nonsteroidal anti-inflammatory drugs, aspirin, simvastatin, estrogen, or a tendency for angioedema (such as in patients with recurrent or episodic idiopathic angioedema) on lowering the threshold for angioedema or increasing the severity of the angioedema episode or episodes after starting ACE inhibitor therapy remains unknown.

Physicians should also be aware of angioedema as a significant side effect of the new renin inhibitor aliskiren (marketed by Novartis Pharmaceuticals as Rasilez in the United Kingdom and as Tekturna in the United States) for treatment of essential hypertension.⁴ A pooled analysis of 31 studies in 12,188 patients showed the incidence of angioedema associated with aliskiren monotherapy to be 0.4%, similar to that with ACE inhibitors: relative risk 0.31, 95% confidence interval 0.07–1.47 for 150 mg; relative risk 0.57, 95% confidence interval 0.17–1.89 for 300 mg).⁵ However, no patients were hospitalized with a serious angioedema event.

Although the mechanism of action of aliskiren via renin inhibition would suggest that bradykinin may not be the causative agent of angioedema, physicians should ensure that patients who report significant angioedema episodes or those who present with angioedema have their medication history thoroughly reviewed to prevent a serious untoward event.

In Reply: We agree with Dr. Khan that the duration of ACE inhibitor therapy should never be used to rule out ACE inhibitor-associated angioedema. In an Italian study of 85 cases of angioedema with ACE inhibitor therapy, the mean ACE inhibitor exposure was a full 12 months before angioedema was diagnosed.¹ More disturbing was the fact that another 12 months elapsed before the ACE inhibitor actually was discontinued. This would indicate that neither the patient nor the physician related the angioedema to ACE inhibitor therapy. In patients with visceral angioedema, since the diagnosis is unusually challenging, even a further delay can be expected.

Angioedema has been reported with aliskiren, but the 0.04% incidence reported by White et al² may reflect very simply that physicians are more alert and on the lookout now more than they ever were when ACE inhibitors were first available. Obviously, greater awareness will lead to more frequent diagnosis. As Dr. Khan points out, there is no known mechanism by which aliskiren should cause angioedema, whereas there is fairly solid evidence that ACE inhibitor-associated angioedema is mediated by bradykinin.^3,4

In Reply: We agree with Dr. Khan that the duration of ACE inhibitor therapy should never be used to rule out ACE inhibitor-associated angioedema. In an Italian study of 85 cases of angioedema with ACE inhibitor therapy, the mean ACE inhibitor exposure was a full 12 months before angioedema was diagnosed.¹ More disturbing was the fact that another 12 months elapsed before the ACE inhibitor actually was discontinued. This would indicate that neither the patient nor the physician related the angioedema to ACE inhibitor therapy. In patients with visceral angioedema, since the diagnosis is unusually challenging, even a further delay can be expected.

Angioedema has been reported with aliskiren, but the 0.04% incidence reported by White et al² may reflect very simply that physicians are more alert and on the lookout now more than they ever were when ACE inhibitors were first available. Obviously, greater awareness will lead to more frequent diagnosis. As Dr. Khan points out, there is no known mechanism by which aliskiren should cause angioedema, whereas there is fairly solid evidence that ACE inhibitor-associated angioedema is mediated by bradykinin.^3,4

In Reply: We agree with Dr. Khan that the duration of ACE inhibitor therapy should never be used to rule out ACE inhibitor-associated angioedema. In an Italian study of 85 cases of angioedema with ACE inhibitor therapy, the mean ACE inhibitor exposure was a full 12 months before angioedema was diagnosed.¹ More disturbing was the fact that another 12 months elapsed before the ACE inhibitor actually was discontinued. This would indicate that neither the patient nor the physician related the angioedema to ACE inhibitor therapy. In patients with visceral angioedema, since the diagnosis is unusually challenging, even a further delay can be expected.

Angioedema has been reported with aliskiren, but the 0.04% incidence reported by White et al² may reflect very simply that physicians are more alert and on the lookout now more than they ever were when ACE inhibitors were first available. Obviously, greater awareness will lead to more frequent diagnosis. As Dr. Khan points out, there is no known mechanism by which aliskiren should cause angioedema, whereas there is fairly solid evidence that ACE inhibitor-associated angioedema is mediated by bradykinin.^3,4

If you get up more than once every night to empty your bladder, you should tell your doctor. He or she may be able to do something about it.

Many people get this problem as they get older. It even has a medical name: nocturia (noct = night, uria = urination). However, it is not something you just have to put up with.

What causes nocturia?

A large urine output can be a sign of a number of diseases. Diabetes, for example, is high on the list and not something you should ignore.

Less room in the bladder, overactive bladder, or an enlarged prostate gland can also make you have to go to the bathroom more often. There are drugs that can help with this. Another common cause is urinary tract infection.

Poor sleep. If you keep waking up for other reasons, you may be getting up just because you are awake. Your doctor may be able to suggest treatments to help you sleep better.

Dear Diary…

To help figure out what is causing the problem, your doctor may ask you to keep a “voiding diary” (a urination diary) for a few days to a week. This means you’ll have to measure everything that comes out—every time—and write down the amount and time. Some people use a special plastic measuring container that fits in the toilet.

Some common-sense advice

• Don’t drink a lot before you go to bed, especially alcoholic or caffeinated drinks.
• If you take a diuretic (water pill) for your blood pressure or heart, don’t take it right before you go to bed.
• If your feet and ankles swell, try wearing compression stockings during the day, and sitting with your legs up in the afternoon.
• Get some moderate exercise every day, such as walking.
• Bed is for sleeping. Avoid reading or watching TV when you’re in bed. Keep the bedroom dark and quiet, if possible. And if it’s cold, put another blanket on the bed.

Be safe

To avoid the risk of tripping and falling down on the way to and from the bathroom, make sure that the path is clear before you go to bed. Clean up the clutter. Get rid of throw rugs. Keep a nightlight on so you can see where you are going. Try to discourage your dog or cat from sleeping in the path you’re going to take. Wear slippers that don’t slip.

It may not be possible to make the problem go away completely, but you may be able to improve it. And if you can sleep better, you’ll probably feel better in the daytime too.

This information is provided by your physician and the Cleveland Clinic Journal of Medicine. It is not designed to replace a physician’s medical assessment and judgment.

This page may be reproduced noncommercially to share with patients. Any other reproduction is subject to Cleveland Clinic Journal of Medicine approval. Bulk color reprints are available by calling 216-444-2661.

For patient information on hundreds of health topics, see the Web site, www.clevelandclinic.org/health.

If you get up more than once every night to empty your bladder, you should tell your doctor. He or she may be able to do something about it.

Many people get this problem as they get older. It even has a medical name: nocturia (noct = night, uria = urination). However, it is not something you just have to put up with.

What causes nocturia?

A large urine output can be a sign of a number of diseases. Diabetes, for example, is high on the list and not something you should ignore.

Less room in the bladder, overactive bladder, or an enlarged prostate gland can also make you have to go to the bathroom more often. There are drugs that can help with this. Another common cause is urinary tract infection.

Poor sleep. If you keep waking up for other reasons, you may be getting up just because you are awake. Your doctor may be able to suggest treatments to help you sleep better.

Dear Diary…

To help figure out what is causing the problem, your doctor may ask you to keep a “voiding diary” (a urination diary) for a few days to a week. This means you’ll have to measure everything that comes out—every time—and write down the amount and time. Some people use a special plastic measuring container that fits in the toilet.

Some common-sense advice

• Don’t drink a lot before you go to bed, especially alcoholic or caffeinated drinks.
• If you take a diuretic (water pill) for your blood pressure or heart, don’t take it right before you go to bed.
• If your feet and ankles swell, try wearing compression stockings during the day, and sitting with your legs up in the afternoon.
• Get some moderate exercise every day, such as walking.
• Bed is for sleeping. Avoid reading or watching TV when you’re in bed. Keep the bedroom dark and quiet, if possible. And if it’s cold, put another blanket on the bed.

Be safe

To avoid the risk of tripping and falling down on the way to and from the bathroom, make sure that the path is clear before you go to bed. Clean up the clutter. Get rid of throw rugs. Keep a nightlight on so you can see where you are going. Try to discourage your dog or cat from sleeping in the path you’re going to take. Wear slippers that don’t slip.

It may not be possible to make the problem go away completely, but you may be able to improve it. And if you can sleep better, you’ll probably feel better in the daytime too.

This information is provided by your physician and the Cleveland Clinic Journal of Medicine. It is not designed to replace a physician’s medical assessment and judgment.

This page may be reproduced noncommercially to share with patients. Any other reproduction is subject to Cleveland Clinic Journal of Medicine approval. Bulk color reprints are available by calling 216-444-2661.

For patient information on hundreds of health topics, see the Web site, www.clevelandclinic.org/health.

If you get up more than once every night to empty your bladder, you should tell your doctor. He or she may be able to do something about it.

Many people get this problem as they get older. It even has a medical name: nocturia (noct = night, uria = urination). However, it is not something you just have to put up with.

What causes nocturia?

A large urine output can be a sign of a number of diseases. Diabetes, for example, is high on the list and not something you should ignore.

Less room in the bladder, overactive bladder, or an enlarged prostate gland can also make you have to go to the bathroom more often. There are drugs that can help with this. Another common cause is urinary tract infection.

Poor sleep. If you keep waking up for other reasons, you may be getting up just because you are awake. Your doctor may be able to suggest treatments to help you sleep better.

Dear Diary…

To help figure out what is causing the problem, your doctor may ask you to keep a “voiding diary” (a urination diary) for a few days to a week. This means you’ll have to measure everything that comes out—every time—and write down the amount and time. Some people use a special plastic measuring container that fits in the toilet.

Some common-sense advice

• Don’t drink a lot before you go to bed, especially alcoholic or caffeinated drinks.
• If you take a diuretic (water pill) for your blood pressure or heart, don’t take it right before you go to bed.
• If your feet and ankles swell, try wearing compression stockings during the day, and sitting with your legs up in the afternoon.
• Get some moderate exercise every day, such as walking.
• Bed is for sleeping. Avoid reading or watching TV when you’re in bed. Keep the bedroom dark and quiet, if possible. And if it’s cold, put another blanket on the bed.

Be safe

To avoid the risk of tripping and falling down on the way to and from the bathroom, make sure that the path is clear before you go to bed. Clean up the clutter. Get rid of throw rugs. Keep a nightlight on so you can see where you are going. Try to discourage your dog or cat from sleeping in the path you’re going to take. Wear slippers that don’t slip.

It may not be possible to make the problem go away completely, but you may be able to improve it. And if you can sleep better, you’ll probably feel better in the daytime too.

This information is provided by your physician and the Cleveland Clinic Journal of Medicine. It is not designed to replace a physician’s medical assessment and judgment.

This page may be reproduced noncommercially to share with patients. Any other reproduction is subject to Cleveland Clinic Journal of Medicine approval. Bulk color reprints are available by calling 216-444-2661.

For patient information on hundreds of health topics, see the Web site, www.clevelandclinic.org/health.

Cervical cancer screening and prevention have evolved rapidly in the last decade, especially in the 5 years since the introduction of the first cancer prevention vaccine, human papillomavirus (HPV) recombinant vaccine.¹

Providers need to understand the rationale for the recommendations so that they can explain them to patients. In particular, patients may wonder why we now begin screening for cervical cancer later than we used to, and why some women do not need to be screened as often. Both of these changes result from our enhanced understanding of the role of HPV in cervical cancer genesis.

In this article we will briefly review:

• The current understanding of the natural history of cervical cancer
• Advantages and disadvantages of cervical cytology, ie, the Papanicolaou (Pap) test
• The role of HPV testing in cervical cancer screening
• The latest screening guidelines (the new standard of care)
• A possible future screening strategy
• The impact of HPV vaccination on screening.

500,000 NEW CASES EVERY YEAR

The incidence of cervical cancer and its mortality rate have decreased more than 50% in the United States over the past 3 decades, largely as a result of screening with the Pap test.² In 2010, there were an estimated 12,200 new cases of invasive cervical cancer in the United States and 4,210 deaths from it,³ which are lower than the historical rates.

However, because most developing countries lack effective screening programs, cervical cancer remains the second-leading cause of death from cancer in women worldwide. According to a recent estimate, there are almost 500,000 new cases and 240,000 deaths from this disease worldwide every year.⁴ If effective global screening programs could be set up, they would markedly reduce the incidence of cervical cancer and deaths from it.⁵

HPV IS NECESSARY BUT NOT SUFFICIENT FOR CERVICAL CANCER TO DEVELOP

For cervical cancer to develop, the essential first step is infection of the cervical epithelium with one of the oncogenic (high-risk) types of HPV (see below).^6–10 Walboomers et al⁹ tested cervical tissue samples taken from 932 women with cervical cancer and detected HPV DNA in 930 (99.8%) of them.

Fortunately, most HPV-infected women do not develop cervical cancer, as most young women clear the infection in an average of 8 to 24 months.^11,12 However, if the infection persists, and if it is one of the high-risk types of HPV, precursor lesions can develop that can progress to cervical cancer.¹³ The evidence conclusively supports the association between oncogenic HPV infection and the subsequent development of virtually all cases of cervical cancer.^6–10

Known risk factors for HPV persistence and the subsequent development of high-grade lesions are cigarette smoking and a compromised immune system.^14,15

Terminology: Results of Pap smears

• Normal
• Atypical squamous cells of undetermined significance (ASC-US)
• Low-grade squamous intraepithelial lesions (LSIL)
• High-grade squamous intraepithelial lesions (HSIL)
• Cancer.

Terminology: Results of cervical biopsy

• Normal
• Cervical intraepithelial neoplasia grade 1 (CIN1)
• CIN2 (previously called moderate dysplasia)
• CIN3 (previously called severe dysplasia)
• Carcinoma in situ
• Invasive cervical cancer.

Lesions that are CIN2 or higher are considered high-grade.¹³

The 18 high-risk HPV types

More than 40 types of HPV infect the genital tract¹⁶; 18 of these (types 16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 73, and 82) are classified as high-risk because of their causative association with cervical cancer (ie, their oncogenic potential).¹⁷

How HPV causes cervical cancer

In laboratory cultures, normal human cells die out after a few generations. However, if human epithelial cells are infected by one of the high-risk types of HPV, they can go on dividing indefinitely.^18,19

Two HPV proteins, E6 and E7, induce this cell “immortalization.”^20,21 E6 from high-risk HPV binds to the human tumor-suppressor protein p53 and rapidly degrades it in a proteolytic process. The p53 protein normally suppresses cell proliferation by arresting growth in the G1 phase of the cell cycle. Therefore, with less p53, the cell cannot suppress uncontrolled cell growth.^22–24

Similarly, E7 from high-risk HPV forms a complex with another human tumor suppressor, the retinoblastoma protein (pRB), and disrupts its binding to a transcriptional factor, E2F-1. The freed E2F-1 then stimulates DNA synthesis and uncontrolled cell growth.²⁵

Furthermore, HPV-16 E6 and E7 proteins can collectively cause cellular genetic instability.²⁶

The carcinogenic mechanism of high-risk HPV is complex. The host immune system and natural tumor suppression play important roles. However, the natural history of cervical intraepithelial neoplasia is not well understood. For example, it remains unclear if low-grade lesions such as CIN1 are necessary precursors to high-grade lesions and invasive cancer.^6,7,10

THE PAP TEST: SPECIFIC BUT NOT VERY SENSITIVE, AND PRONE TO ERROR

The principal advantage of cervical cytologic testing (ie, the Pap test) in detecting cervical dysplasia is its overall high specificity. Many studies have found that the specificity of conventional Pap testing can reach approximately 98%.²⁷

However, the conventional Pap test has drawbacks. Contaminants such as blood, discharge, and lubricant can make it difficult to interpret, and artifact can occur with air-drying of the Pap smear as it is transferred to the cell slide (“air-drying artifact”).

Liquid-based cytologic study has replaced the older method

To overcome these disadvantages, a liquid-based method of cervical cytologic study, ThinPrep (Hologic, Bedford, MA), was introduced in the mid-1990s. In this method, cell samples are first transferred to a liquid solution for mechanical separation from contaminants, and a representative sample of cells is then placed on a slide for review.

The liquid-based method filters out most contaminating blood, inflammatory cells, and debris. It also eliminates the air-drying artifact in the conventional Pap collection technique and improves specimen adequacy. Cytotechnologists find liquid-based specimens easier to read because the cells are more evenly distributed on a clearer background. Another advantage is that we can routinely test for HPV in the available residual specimen if the cytologic interpretation is abnormal.

The main disadvantages of the liquid-based method are that its specificity is lower than that of conventional Pap smears (around 78%) and that it costs more.²⁸ Nevertheless, the liquid-based technique has become the main method of cervical cytology, used by nearly 90% of gynecologists in the United States since 2003.¹

Cytology is still prone to false-negative results

Despite the success of both conventional Pap testing and liquid-based Pap testing, cervical cytology is inherently prone to sample-quality variation, subjective interpretation error, and false-negative results. False-negative results can be due to failure to transfer dysplastic cells to the slide or failure of the cytologist to recognize abnormal cells. In 30% of new cases of cervical cancer, the patient had recently had a Pap test that was interpreted as negative.^1,29

Errors in interpretation are exacerbated by inconsistency among cytopathologists. In one study,^6,30 when a group of quality-control pathologists reviewed nearly 5,000 cytology specimens, they came to the same conclusion that the original reviewers did more than 50% of the time only for negative and LSIL readings. Of the specimens initially reported as ASC-US, almost 40% were reclassified as negative on further review. Of those originally interpreted as HSIL, more than 50% were reclassified as LSIL, as ASC-US, or as negative.

Furthermore, many studies found that the sensitivity of conventional Pap testing was only around 50%.²⁷ The new liquid-based Pap test uses computer imaging, which has improved the rate of detection of cervical dysplasia but may still miss 15% to 35% of cases of HSIL (severe dysplasia) or cancer.³¹ Failure to detect cervical dysplasia or cancer on Pap smear has led to a number of lawsuits.³²

Clearly, with its relatively low sensitivity, cervical cytology is no longer good enough to use as a sole screening test in all situations. However, its high specificity is an advantage when it is combined with HPV testing in screening.

HPV TESTING AND PAP TESTING COMPLEMENT EACH OTHER

From 17% to 36% of HPV-infected women develop a cytologic abnormality within 5 years, compared with 4% to 15% of women who are HPV-negative.^33,34

The usefulness of testing for HPV in women who have had an abnormal Pap test has been well demonstrated in multiple studies.^35–38

The landmark Atypical Squamous Cells of Undetermined Significance/Low-Grade Squamous Intraepithelial Lesions Triage Study (ALTS)³⁹ found that 82.9% of women with LSIL were HPV-positive. The investigators concluded that HPV testing has little utility in women with LSIL, as the test would likely be positive and thus would not change the decision to perform colposcopy.

However, in women with ASC-US, the sensitivity of HPV testing for predicting CIN3 or cancer was 96.3% and the negative predictive value was 99.5%. In contrast, the sensitivity of a single repeat Pap test was only 44.1%. This large randomized trial conclusively validates the important role of HPV testing in triaging women with ASC-US.

More recently, a meta-analysis of 20 studies of HPV testing in women with ASC-US found that it had a sensitivity of 92.5% and a specificity of 62.5% for detecting CIN2 or worse lesions, and a sensitivity of 95.6% and a specificity of 59.2% for detecting CIN3 or worse lesions.⁴⁰

Furthermore, HPV testing in primary cervical cancer screening is strongly supported by large cross-sectional studies^41–45 and randomized clinical trials.^46,47 These studies have conclusively shown that HPV testing is significantly more sensitive than Pap testing for detecting cervical intraepithelial neoplasia, and that, when combined with Pap testing, it can achieve nearly 100% clinical sensitivity and nearly 93% specificity in women age 30 or older. Women who have negative results on both the HPV test and the Pap test can be reassured that their risk of undetected CIN2, CIN3, or cervical cancer is extremely low, since HPV testing has a negative predictive value close to 100%.⁴⁶

In large multinational European studies involving more than 24,000 women, the risk of CIN3 or cancer after 6 years of follow-up was only 0.28% in women who had negative results on both HPV and Pap testing at baseline. This rate was basically the same as in women who tested negative for HPV alone (0.27%). However, it was significantly lower than that of all women who had negative Pap test results (0.97%). The combination of HPV testing and Pap testing at 6-year intervals offered better protection than Pap testing alone at 3-year intervals.⁴⁸

NEW STANDARD OF CARE: THE LATEST SCREENING GUIDELINES

Until the mid-1990s, the strategy for cervical cancer screening had remained largely unchanged for many years. Since then, several advances have prompted changes in the standard of care.

1996—The US Food and Drug Administration (FDA) approved liquid-based Thin-Prep for cervical cancer screening, which improved specimen adequacy and reduced ambiguous interpretations compared with the original slide-based method of collection.⁴⁹

2001—The Bethesda terminology for reporting cervical cytology results was updated. First proposed in 1988 to replace the original Papanicolaou system and revised in 1991, this standardized terminology enabled better clinical decision-making.⁵⁰

2001—The FDA approved HPV testing for women with ASC-US. This provided a better triage strategy for deciding which women need colposcopy to exclude true intraepithelial lesions. Following the FDA approval, the clinical effectiveness of HPV testing in women with ASC-US was validated by a large randomized clinical trial—the ALTS.⁵¹

2003—The FDA approved HPV testing in conjunction with Pap testing for women age 30 or older in routine primary screening.⁵²

Guidelines available

Based on these new developments in technology and reporting terminology, and the incorporation of HPV testing, several organizations issued guidelines.

The American Society for Colposcopy and Cervical Pathology published a consensus guideline on management of abnormal cervical cytology in 2001 and revised it in 2006.⁵³

The American Cancer Society issued its guideline for cervical cancer screening in 2002.⁵⁴

The US Preventive Services Task Force published its screening guidelines in 2003.⁵⁵

The American College of Obstetricians and Gynecologists (ACOG) also made new recommendations in 2003 and updated them in December 2009.¹

Start screening at age 21

Cervical cancer screening should begin at age 21 regardless of the age of onset of vaginal intercourse, according to the 2009 ACOG guidelines.¹ This represents a change from previous recommendations from ACOG, the American Cancer Society, and the US Preventive Services Task Force, which were to start screening within 3 years of the onset of vaginal intercourse.

Rationale. This latest recommendation is based on the high rates of clearance of HPV infection and of spontaneous dysplasia regression and the low incidence of cervical cancer in younger women.^57,58 HPV infections are common in young women who have had vaginal intercourse. However, most such HPV infections are cleared by the immune system within 1 to 2 years without causing cervical dysplasia.^11,12 Invasive cervical cancer in women younger than 21 years is very rare. The annual incidence is only one to two cases per 1 million women ages 15 to 19.^2,55

Another reason for not screening before age 21 is that a positive test result may lead to unnecessary anxiety and potentially harmful evaluations and procedures.

Screening intervals extended

The 2009 ACOG guidelines lengthen the cervical cancer screening interval to every 2 years in women under age 30.¹ (The 2003 ACOG guidelines said to screen every year.)

For women age 30 and older, the 2009 ACOG guidelines recommend extending the interval to every 3 years when combined Pap and HPV testing are negative (changed from every 2 to 3 years).¹

Rationale. Studies have shown little advantage in screening every year in women under the age of 30, with no higher risk of cervical cancer in women screened at a 2- to 3-year interval.^59–62 The absolute risk of cervical cancer in a well-screened population is very low.⁶³ Moreover, the absolute number of cervical cancer cases in women age 30 to 64 years screened at 3-year intervals is only four per 100,000 women.⁶⁴

HPV-plus-Pap testing for women over 30

Based on convincing evidence of the high sensitivity and the high negative predictive value of HPV testing, since 2003 ACOG had recommended HPV-plus-Pap testing in women over age 30. Its 2009 guidelines upgraded this recommendation to level A, ie, the highest grade, based on good and consistent scientific evidence.¹ (Previously the recommendation was level B.)

The American Cancer Society also recommends combined HPV and Pap testing as the optimal screening approach in women age 30 or older, with the subsequent screening interval 3 years if both tests are negative. It also endorses Pap testing alone every 2 to 3 years as an alternative screening strategy in this age group.

The US Preventive Services Task Force recommends Pap testing every 3 years in women age 30 or older, and it does not recommend for or against HPV testing. However, neither the US Preventive Services Task Force nor the American Cancer Society has updated its guidelines in 8 years.

Rationale. Women who undergo HPV-plus-Pap testing and who test negative on both are at very low risk of developing CIN2 or CIN3 during the next 4 to 6 years. The risk is much lower than that for women who have a sole negative Pap test result.^39,40 Because of this extremely high negative predictive value, women age 30 and older who had negative results on both Pap and HPV testing should be screened no more often than every 3 years.

We believe that the HPV-plus-Pap testing strategy recommended by the 2009 ACOG guidelines for women age 30 and older is the most effective screening approach. This strategy takes advantage of the high sensitivity and high negative predictive value of HPV testing, as well as the high specificity of Pap testing. It achieves almost 100% clinical sensitivity in detecting cervical dysplasia.⁴⁶

The 2009 ACOG guidelines for the first time call for stopping cervical cancer screening in women 65 to 70 years of age who have had three negative Pap tests in a row and no abnormal tests in the previous 10 years.¹ The American Cancer Society recommends stopping screening at age 70,⁶⁵ while the US Preventive Services Task Force recommends stopping at age 65.⁵⁵

Rationale. Cervical cancer develops slowly, and risk factors tend to decline with age, Also, postmenopausal mucosal atrophy may predispose to false-positive Pap results, which can lead to additional procedures and unnecessary patient anxiety.⁶⁶

However, it is probably reasonable to continue screening in women age 70 and older who are sexually active with multiple partners and who have a history of abnormal Pap test results.¹

Women who have had a hysterectomy

According to the latest American Cancer Society, ACOG, and US Preventive Services Task Force guidelines, cervical cancer screening should be discontinued after total hysterectomy for benign indications in women who have no history of high-grade cervical intraepithelial neoplasia, ie, CIN2 or worse.¹

Rationale. If the patient has no cervix, continued vaginal cytology screening is not indicated, since the incidence of primary vaginal cancer is one to two cases per 100,000 women per year, much lower than that of cervical cancer.⁶⁵

However, before discontinuing screening, clinicians should verify that any Pap tests the patient had before the hysterectomy were all read as normal, that the hysterectomy specimen was normal, and that the cervix was completely removed during hysterectomy.

Be ready to explain the recommendations

It is very important for providers to understand the evidence supporting the latest guidelines, as many patients may not realize the significant technological improvements and improved understanding of the role of HPV in cervical cancer genesis that have resulted in the deferred onset of screening and the longer intervals between screenings. This knowledge gap for patients can result in anxiety when told they no longer need an annual Pap test or can start later, if the issue is not properly and thoroughly explained by a confident provider.

A FUTURE STRATEGY: HPV AS THE SOLE PRIMARY SCREENING TEST?

Since HPV testing is much more sensitive than Pap testing for detecting cervical lesions of grade CIN2 or higher, why not use HPV testing as the primary test and then do Pap testing (which is more specific) only if the HPV test is positive?

Mayrand et al⁴⁶ conducted the first large randomized trial in which HPV testing was compared directly as a stand-alone test with the Pap test in a North American population with access to quality care. Results were published in 2007. In Canada, a total of 10,154 women ages 30 to 69 years in Montreal and St. John’s were randomly assigned to undergo either conventional Pap testing or HPV testing. The sensitivity of HPV testing for CIN2 or CIN3 was 94.6%, whereas the sensitivity of Pap testing was only 55.4%. The specificity was 94.1% for HPV testing and 96.8% for Pap testing. In addition, HPV screening followed by Pap triage resulted in fewer referrals for colposcopy than did either test alone (1.1% vs 2.9% with Pap testing alone or 6.1% with HPV testing alone). In other words, HPV testing was almost 40% more sensitive and only 2.7% less specific than Pap testing in detecting cervical cancer precursors.

However, more controlled trials are needed to validate such a strategy. Furthermore, it remains unclear if a change from Pap testing to a primary HPV testing screening strategy will further reduce the mortality rate of cervical cancer, since the burden of cervical cancer worldwide lies in less-screened populations in low-resource settings.

Dillner et al,⁴⁸ in a 2008 European study, further demonstrated that HPV testing offers better long-term (6-year) predictive value for CIN3 or worse lesions than cytology does. These findings suggest that HPV testing, with its higher sensitivity and negative predictive value and its molecular focus on cervical carcinogenesis, may safely permit longer screening intervals in a low-risk population.

Sankaranarayanan et al⁷² performed a randomized trial in rural India in which 131,746 women age 30 to 59 years were randomly assigned to four groups: screening by HPV testing, screening by Pap testing, screening by visual inspection with acetic acid, and counseling only (the control group). At 8 years of follow-up, the numbers of cases of cervical cancer and of cervical cancer deaths were as follows:

• With HPV testing: 127 cases, 34 deaths
• With Pap testing: 152 cases, 54 deaths
• With visual inspection: 157 cases, 56 deaths
• With counseling only: 118 cases, 64 deaths.

The authors concluded that in a low-resource setting, a single round of HPV testing was associated with a significant reduction in the number of deaths from cervical cancer. Not only did the HPV testing group have a lower incidence of cancer-related deaths, there were no cancer deaths among the women in this group who tested negative for HPV. This is the first randomized trial to suggest that using HPV testing as the sole primary cervical cancer screening test may have a benefit in terms of the mortality rate.

At present, to the best of our knowledge, there are no US data validating the role of HPV testing as a stand-alone screening test for cervical cancer.

HPV VACCINATION DOES NOT MEAN THE END OF SCREENING

The development of an effective HPV vaccine and FDA approval of the first quadrivalent (active against HPV 6, 11, 16, and 18) recombinant vaccine (Gardasil) in 2006 has opened a new era of cervical cancer prevention.^73,74 At present, the Advisory Committee on Immunization Practices⁷⁵ recommends vaccination for females 9 to 26 years old.

However, HPV vaccination will not make screening obsolete, since not all women will be vaccinated, and those who have already contracted one of these high-risk HPV types will not benefit.^76,77 In addition, the current HPV vaccine does not protect against infection with other oncogenic HPV types. The experts estimate that the initial impact of the HPV vaccine on cervical cancer will not likely be apparent until at least 20 to 30 years after a nationwide vaccination program is implemented.^78,79 Therefore, the HPV vaccine certainly does not portend the end of screening. Vaccination combined with continued screening will provide added benefit for cervical cancer prevention.⁸⁰

The last decade has been an exciting period in the field of cervical cancer screening and prevention, with advances in technology, newly acquired knowledge, and the development of the HPV vaccine. As a result, our clinical practice has become a work in progress, continuing to evolve as we continue to discover more information. The possibility of eradicating cervical cancer has never been greater. The implementation of the most sensitive and effective screening strategy and of a worldwide HPV vaccination program will help us to eventually eradicate cervical cancer and make it a disease of the past.⁸¹