large polyps) Complexity: Intermediate • Full bowel cleansing • Cannot remove polyps or perform biopsies • Exposure to low-dose radiation • Colonoscopy necessary if positive • Not covered by all insurance plans 5 years Flexible sigmoidoscopy • Fairly quick • Few complications • Minimal bowel preparation • Does not require sedation or a specialist Performance: High for rectum & lower one-third of the colon Complexity: Intermediate • Partial bowel cleansing • Views only one-third of colon • Cannot remove large polyps • Small risk of infection or bowel tear • Slightly more effective when combined with annual fecal occult blood testing • Colonoscopy necessary if positive • Limited availability 5 years Stool Tests (Low-sensitivity stool tests, such as single-sample FOBT done in the doctor’s office or toilet bowl tests, are not recommended.) Fecal immunochemical test (FIT) • No bowel cleansing or sedation • Performed at home • Low cost • Noninvasive Performance: Intermediate for cancer Complexity: Low • Requires multiple stool samples • Will miss most polyps • May produce false-positive test results • Slightly more effective when combined with a flexible sigmoidoscopy every five years • Colonoscopy necessary if positive Annual High-sensitivity guaiac-based fecal occult blood test (gFOBT) • No bowel cleansing or sedation • Performed at home • Low cost • Noninvasive Performance: Intermediate for cancer Complexity: Low • Requires multiple stool samples • Will miss most polyps • May produce false-positive test results • Pre-test dietary limitations • Slightly more effective when combined with a flexible sigmoidoscopy every five years • Colonoscopy necessary if positive Annual Multitargeted stool DNA test (Cologuard®) • No bowel cleansing or sedation • Performed at home • Requires only a single stool sample • Noninvasive Performance: Intermediate for cancer Complexity: Low • Will miss most polyps • More false-positive results than other tests • Higher cost than gFOBT and FIT • Colonoscopy necessary if positive 3 years, per manufacturer’s recommendation *Complexity involves patient preparation, inconvenience, facilities and equipment needed, and patient discomfort. †For average-risk individuals, e.g., does not apply to those who have a history of adenoma. Colorectal Cancer Facts & Figures 2020-2022 21 interval cancer).235, 236 Low-quality colonoscopy (measured as low adenoma detection rate) is associated with a higher likelihood of interval CRC and CRC death.236 Flexible sigmoidoscopy Sigmoidoscopy was a common screening test before 2000, but current availability is limited because it has mostly been replaced by colonoscopy (see page 23 for current prevalence of sigmoidoscopy and other screening tests). These tests are very similar except colonoscopy can examine the entire colon whereas sigmoidoscopy can only visualize the rectum and distal one-third of the colon, and must be repeated more often (Table 4). Simple bowel cleansing, usually with enemas, is sufficient to prepare the colon, and the procedure is often performed without sedation in a general health care practitioner’s office. If there is a polyp or tumor present, the patient should be referred for a colonoscopy so that the entire colon can be examined. Recent analysis of data from randomized controlled trials with up to 17 years of follow-up shows that sigmoidoscopy is associated with about a 20%-25% reduction in CRC incidence and a 25%-30% reduction in CRC mortality, with greater reductions in men than women.237-239 Computed tomographic colonography (CTC) Also referred to as virtual colonoscopy, CTC is an imaging procedure that provides 2- or 3-dimensional views of the entire colon and rectum with the use of a special x-ray machine linked to a computer.230 Although a full bowel cleansing is necessary for a successful examination, sedation is not required. A small, flexible tube is inserted into the rectum in order to allow carbon dioxide, or sometimes air, to inflate the colon; then the patient passes through the CT scanner, which creates multiple images of the interior of the colon. CTC is less invasive than colonoscopy or sigmoidoscopy and typically takes approximately 10 to 15 minutes to complete.240