Assessment and Optimization of Phototherapy
After an appropriate starting dosage has been established, patients should be evaluated at each subsequent visit for the degree of treatment response. Excessive erythema (lasting more than 48 hours) or adverse effects, such as itching, stinging, or burning, are indications that the patient should have their dose adjusted back to the last dose without such adverse responses. Because tolerance to treatment develops over time, patients who miss a scheduled dose of NB-UVB phototherapy require their dose to be temporarily lowered. Targeted dosage of UVB phototherapy at a frequency of 2 to 3 times weekly is preferred over treatment 1 to 2 times weekly; however, consideration should be given toward patient preference.26 Dosing may be increased at a rate of 5% to 10% after each treatment, as tolerated, if there is no clearance of skin lesions with the original treatment dose. Patient skin type also is helpful in dictating the maximum phototherapy dose for each patient (Table 3).
Once a patient’s psoriatic lesions have cleared, the patient has the option to taper or indefinitely continue maintenance therapy. The established protocol for patients who choose to taper therapy is treatment twice weekly for 4 weeks, followed by once-weekly treatment for the second month. The maintenance dosage is held constant during the taper. For patients who prefer indefinite maintenance therapy, treatment is administered every 1 to 2 weeks, with a maintenance dosage that is approximately 25% lower than the original maintenance dosage.
Efforts should be made to ensure that the long-term sequalae of phototherapy are minimized (Table 1). Development of cataracts is a recognized consequence of prolonged UVB exposure; therefore, eye protection is recommended during all UVB treatment sessions to reduce the risk for ocular toxicity. Although pregnancy is not a contraindication to phototherapy, except for PUVA, there is a dose-dependent degradation of folate with NB-UVB treatment, so folate supplementation (0.8 mg) is recommended during NB-UVB treatment to prevent development of neural tube defects in fetuses of patients who are pregnant or who may become pregnant.27
Although phototherapy carries the theoretical risk for photocarcinogenesis, multiple studies have shown no increased risk for malignancy with either NB-UVB or BB-UVB phototherapy.22,23 Regardless, patients who develop new-onset skin cancer while receiving any phototherapeutic treatment should discuss the potential risks and benefits of continued treatment with their physician. Providers should take extra caution prior to initiating treatment, especially in patients with a history of cutaneous malignancy. Because oral PUVA is a systemic therapy, it is associated with a greater risk for photocarcinogenesis than any other modality, particularly in fair-skinned individuals. Patients younger than 10 years; pregnant or nursing patients; and those with a history of lupus, xeroderma pigmentosum, or melanoma should not receive PUVA therapy because of their increased risk for photocarcinogenesis and TRAEs.
The decision to switch patients between different phototherapy modalities during treatment should be individualized to each patient based on factors such as disease severity, quality of life, and treatment burden. Other factors to consider include dosing frequency, treatment cost, and logistical factors, such as proximity to a treatment facility. Physicians should have a detailed discussion about the risks and benefits of continuing therapy for patients who develop new-onset skin cancer during phototherapy.
Phototherapy is an effective and safe treatment for patients with psoriasis who have localized and systemic disease. There are several treatment modalities that can be tailored to patient needs and preferences, such as home NB-UVB for patients who are unable or unwilling to undergo office-based treatments. Phototherapy has few absolute contraindications; however, relative contraindications to phototherapy exist. Patients with a history of skin cancer, photosensitivity disorders, and autoimmune diseases (eg, lupus) carry greater risks for adverse events, such as sun-related damage, cancer, and dysplasia. Because these conditions may preclude patients from pursuing phototherapy as a safe and effective approach to treating moderate to severe psoriasis, these patients should be considered for other therapies, such as biologic medications, which may carry a more favorable risk-benefit ratio given that individual’s background.