Evelyn P. Whitlock, MD, MPH; Jennifer S. Lin, MD, MCR; Elizabeth Liles, MD; Tracy L. Beil, MS; Rongwei Fu, PhD
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.
To review evidence related to knowledge gaps identified by the 2002 recommendation and to consider community performance of screening endoscopy, including harms.
MEDLINE, Cochrane Library, expert suggestions, and bibliographic reviews.
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.
Two reviewers verified extracted data.
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.
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.
KQ1: What is the effectiveness of the following screening methods (alone or in combination) in reducing mortality from colorectal cancer? a. Flexible sigmoidoscopy, b. Colonoscopy, c. Computed tomographic (CT) colonography, d. Fecal screening tests: i. High-sensitivity guaiac fecal occult blood test (FOBTs); ii. Fecal immunochemical test; iii. Fecal DNA test. KQ2a: What are the sensitivity and specificity of 1) colonoscopy and 2) flexible sigmoidoscopy when used to screen for colorectal cancer in the community practice setting? KQ2b: What are the test performance characteristics of 1) CT colonography and 2) fecal screening tests (as listed in KQ1d) for colorectal cancer screening, as compared to an acceptable reference standard? KQ3a: What are age-specific rates of harm from colonoscopy and flexible sigmoidoscopy in the community practice setting? KQ3b: What are the adverse effects of newer tests, including 1) CT colonography and 2) fecal screening tests (as listed in KQ1d)?
Appendix Table 1.
Appendix Table 2.
Appendix Table 3.
KQ= key question; SER= standardized evidence review. For list of key questions, see legend for Figure 1.
Appendix Table 4.
Test for heterogeneity for all studies based on logit of proportions using a random-effects model (P= 0.13).
* 95% CIs are exact confidence intervals.
Test for heterogeneity for all studies based on logit of proportions using a random-effects model (P= 0.26).
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Whitlock EP, Lin JS, Liles E, Beil TL, Fu R. Screening for Colorectal Cancer: A Targeted, Updated Systematic Review for the U.S. Preventive Services Task Force. Ann Intern Med. 2008;149:638-658. doi: 10.7326/0003-4819-149-9-200811040-00245
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Published: Ann Intern Med. 2008;149(9):638-658.
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