Screening for Colorectal Cancer: A Targeted, Updated Systematic Review for the U.S. Preventive Services Task Force

In 2002, the U.S. Preventive Services Task Force (USPSTF) recommended colorectal cancer screening for adults 50 years of age or older but concluded that evidence was insufficient to prioritize among screening tests or evaluate newer tests, such as computed tomographic (CT) colonography. PURPOSE: To review evidence related to knowledge gaps identified by the 2002 recommendation and to consider community performance of screening endoscopy, including harms. DATA SOURCES: MEDLINE, Cochrane Library, expert suggestions, and bibliographic reviews. STUDY SELECTION: Eligible studies reported performance of colorectal cancer screening tests or health outcomes in average-risk populations and were at least of fair quality according to design-specific USPSTF criteria, as determined by 2 reviewers. DATA EXTRACTION: Two reviewers verified extracted data. DATA SYNTHESIS: Four fecal immunochemical tests have superior sensitivity (range, 61% to 91%), and some have similar specificity (97% to 98%), to the Hemoccult II fecal occult blood test (Beckman Coulter, Fullerton, California). Tradeoffs between superior sensitivity and reduced specificity occur with high-sensitivity guaiac tests and fecal DNA, with other important uncertainties for fecal DNA. In settings with sufficient quality control, CT colonography is as sensitive as colonoscopy for large adenomas and colorectal cancer. Uncertainties remain for smaller polyps and frequency of colonoscopy referral. We did not find good estimates of community endoscopy accuracy; serious harms occur in 2.8 per 1000 screening colonoscopies and are 10-fold less common with flexible sigmoidoscopy. LIMITATION: The accuracy and harms of screening tests were reviewed after only a single application.

Fecal tests with better sensitivity and similar specificity are reasonable substitutes for traditional fecal occult blood testing, although modeling may be needed to determine all tradeoffs. Computed tomographic colonography seems as likely as colonoscopy to detect lesions 10 mm or greater but may be less sensitive for smaller adenomas. Potential radiation-related harms, the effect of extracolonic findings, and the accuracy of test performance of CT colonography in community settings remain uncertain. Emphasis on quality standards is important for implementing any operator-dependent colorectal cancer screening test.