On the basis of the review of the available guidelines, the American College of Physicians (ACP) concludes:
Guidance Statement 1: ACP recommends that clinicians perform individualized assessment of risk for colorectal cancer in all adults.
Clinicians should perform individualized assessment of colorectal cancer risk in all adults to help in deciding when to begin screening. Risks for colorectal cancer include age, race, and family history (for example, diagnosis of colorectal cancer, hereditary nonpolyposis, or familial adenomatous polyposis). Diagnosis of colorectal cancer in a first-degree relative, especially before age 50 years, increases the probability of colorectal cancer in all adults; a thorough family history, including the age of diagnosis of colorectal cancer for primary and secondary relatives, is important for assessing this risk. African Americans have the highest incidence of colorectal cancer compared with other races.
Guidance Statement 2: ACP recommends that clinicians screen for colorectal cancer in average-risk adults starting at the age of 50 years and in high-risk adults starting at the age of 40 years or 10 years younger than the age at which the youngest affected relative was diagnosed with colorectal cancer.
The evidence in the reviewed guidelines shows that colorectal cancer screening helps to identify undiagnosed premalignant lesions and reduces mortality with the provision of timely treatment. The benefit of reduced mortality outweighs the harms of screening for colorectal cancer in average-risk adults starting at age 50 years and high-risk adults starting at age 40 years or 10 years younger than the age at which the youngest affected relative was diagnosed.
Guidance Statement 3: ACP recommends using a stool-based test, flexible sigmoidoscopy, or optical colonoscopy as a screening test in patients who are at average risk. ACP recommends using optical colonoscopy as a screening test in patients who are at high risk. Clinicians should select the test based on the benefits and harms of the screening test, availability of the screening test, and patient preferences.
Shared decision making is important when selecting a screening test because the currently available colorectal cancer screening tests are believed to be similarly efficacious. Clinicians should discuss the benefits, harms, effectiveness, safety, and costs of the options available to screen for colorectal cancer. The sensitivity, specificity, costs, benefits, harms, and screening intervals for the tests are described in Table 2 in the original guideline document. The test quality also varies on the basis of the skill of the person performing the test (for example, ensuring correct stool preparation or having an experienced professional perform a colonoscopy), and stool-based test quality can also depend on the samples collected by the patient. Harms of endoscopic and radiologic screening tests include perforation and major bleeding with endoscopic tests and exposure to radiation with radiologic tests. Although few studies have evaluated the harms of stool-based tests, the probability of major harms is probably very small. The choice of test may also need to be made on the basis of the local availability of screening methods. For example, accessibility to endoscopic tests varies by region in the United States.
The screening interval for average-risk adults older than 50 years is 10 years for colonoscopy; 5 years for flexible sigmoidoscopy, double-contrast barium enema (DCBE), and computed tomography colonography (CTC); annually for guaiac-based fecal occult blood test (gFOBT) and immunochemical-based fecal occult blood test (iFOBT); and uncertain for stool DNA (sDNA).
Although optical colonoscopy is generally regarded as the gold standard, it has limitations, including a false-negative rate of 10% to 20%. Also, evidence is not clear on the optimal frequency of screening using colonoscopy, but in average-risk patients, 10 years is usually regarded as a safe interval. Colonoscopy should be used as a follow-up for positive test results regardless of the noncolonoscopic screening test used. In patients who are at high risk because of family history, the American College of Gastroenterology (ACG) recommends screening every 5 years.
Computed tomography colonography is an option for screening in average-risk patients older than 50 years and is supported by some guidelines. However, the U.S. Preventive Services Task Force (USPSTF) found that the evidence is insufficient to assess the benefits and harms of CTC.
Guidance Statement 4: ACP recommends that clinicians stop screening for colorectal cancer in adults over the age of 75 years or in adults with a life expectancy of less than 10 years.
The harms of screening for colorectal cancer seem to outweigh the benefits in most adults older than 75 years or in adults who have a life expectancy of less than 10 years. Therefore, clinicians should not screen adults older than 75 years or those with substantial comorbid conditions (for example, diabetes, cardiopulmonary diseases, and stroke) with a life expectancy of less than 10 years.