Cancer screening is an important example of secondary prevention—the aim being to detect disease at an early stage, when treatment can prevent symptomatic disease. Over the years, screening tests for breast cancer, colorectal cancer (CRC), cervical cancer, and, most recently, lung cancer have been developed and recommended by the U.S. Preventive Services Task Force (USPSTF). Among breast cancer, cervical cancer, and CRC, the screening rate for CRC remains lowest, at 58.6%.1
The importance of screening for CRC is highlighted by the facts that:
- CRC is the third most commonly diagnosed form of cancer in the United States among both men and women
- CRC is the second leading cause of cancer-related death.2
The overall decrease in the incidence of CRC in the United States has been credited to improvements in screening and removal of potentially precancerous lesions.3
Harmful disparity puts the mentally ill at exceptional risk
Screening patterns for CRC among patients with mental illness are poorly characterized, but it is known that the overall cancer screening rate among patients with severe psychiatric illness lags significantly behind the rate in the general population.4,5 In addition, studies have shown that mortality among patients with CRC who have a mental disorder is elevated, compared with CRC patients who do not have a psychiatric diagnosis.6
Why this disparity? It might be that CRC is more likely to be diagnosed at an advanced stage among these patients, or that they are less likely to receive cancer treatment after diagnosis, or are more likely to have a longer delay between diagnosis and initial treatment than patients who do not have a psychiatric diagnosis.7
Regardless, psychiatric practitioners can make a significant impact on reducing this health disparity by leveraging their unique therapeutic relationship to educate patients about screening options and dispel myths about cancer screening. In this article, we outline practical strategies for CRC screening and weigh the advantages and disadvantages for the use of several tools and guidelines in psychiatric patients.
What is the pathogenesis of colorectal cancer?
Most cases of CRC evolve from polyps, abnormal growths on the lining of the colon or rectum. Constituting an estimated 96% of all polyps, adenomas are by far the most common form in the colon and rectum.
Adenomas also are most likely to transform over time to dysplasia, and then to progress to cancer.8 Although all adenomas have malignant potential, <10% evolve to adenocarcinoma. This proposed adenoma➝carcinoma sequence is not well understood; however, it is known that CRC usually develops slowly—over 10 to 15 years.9 Detection and removal of adenomas and treatable, localized carcinomas form the basis of screening for CRC.
Risk factors for colorectal cancer
A number of risk factors for CRC have been identified.
Specific heritable conditions, such as Lynch syndrome and familial adenomatous polyposis, pose the greatest risk of CRC, particularly at younger ages and compared with people without such a history.10
Family history. One of the strongest risk factors for CRC remains a family history of the disease. People who have a first-degree relative with a diagnosis of CRC are at 2 to 3 times the risk of CRC, compared with people without a family history of the disease. This risk increases further if multiple family members are affected or if the diagnosis was made in a relative at a young age.11,12
Other non-modifiable risk factors include a personal history of inflammatory bowel disease, type 2 diabetes mellitus, male sex, African American heritage, and increasing age.13-15
Common modifiable risk factors include obesity, smoking, and alcohol consumption.16-18
What is the role of screening?
CRC screening is only appropriate for patients who are asymptomatic. CRC generally is asymptomatic in early stages. Prognosis also is most favorable when CRC is detected in the asymptomatic stage.
As lesions of CRC grow, the presentation might include hematochezia, melena, abdominal pain, weight loss, occult anemia, constipation or diarrhea, and changes in stool caliber.19 These signs and symptoms are not highly specific for CRC, however, and might be indicative of other gastrointestinal pathology, including inflammatory bowel disease, diverticulitis, irritable bowel syndrome, infectious colitis, hemorrhoids, and mesenteric ischemia.
Symptomatic patients should be referred directly for diagnostic evaluation. Colonoscopy with biopsy is the standard for diagnosing CRC. Once a diagnosis of CRC is made, patients should be referred to a specialist to discuss treatment; options largely depend on the stage of the cancer at diagnosis.
What screening tests are available?
Unlike screening for other cancers, there are a number of reasonable options for CRC screening; Table 115 compares their relative pros and cons. Each test has its benefits and drawbacks, allowing the screening strategy to be customized based on patient preference and characteristics, but this variability also can lead to confusion by patient and provider about those options.
Stool-based tests detect trace amounts of blood from early-stage treatable cancers. Highly sensitive fecal occult blood testing (FOBT) has been shown specifically to decrease mortality from CRC.20 Stool-based tests are inexpensive and noninvasive, but require: