Clinical Inquiries. How does colonoscopy compare with fecal occult blood testing as a screening tool for colon cancer?

■ Evidence summary A Cochrane review conducted a metaanalysis looking only at FOBT for colorectal cancer screening. This review, based on published and unpublished data from 5 controlled trials, demonstrated that 3-card home FOBT conferred a reduction in colorectal cancer mortality of 16% (relative risk [RR]=0.84; 95% confidence interval [CI], 0.77–0.92) and a number needed to screen of 1173 (95% CI, 741–2807) to prevent 1 death from colon cancer over a 10-year period. If adjusted for adherence to screening, the reduction in mortality increased to 23% (RR=0.77; 95% CI, 0.57–0.89). In addition, long-term follow up of one of the RCTs in the review showed a continued reduction in colorectal cancer mortality of 34% (RR=0.66; 95% CI, 0.54–0.81) in subjects adhering to the FOBT screening protocol over a 13-year interval. Overall mortality did not differ between the screened and unscreened groups. A systematic review performed for the US Preventive Services Task Force (USPSTF) incorporated more recent data on colorectal cancer screening including colonoscopy. This review reached similar conclusions as above. This review also looked at office FOBT performed after digital rectal exam. It is important to note that No studies have directly compared colonoscopy with fecal occult blood testing (FOBT). Multiple screening trials have demonstrated that a primary strategy of 3-card home FOBT with follow-up colonoscopy for positive results is associated with a significant reduction in mortality from colorectal cancer (strength of recommendation [SOR]: A, based on systematic reviews of randomized and nonrandomized controlled trials). A single negative office-based digital FOBT does not decrease the likelihood of advanced neoplasia (SOR: B, based on a single prospective cohort study). There are no publications of screening trials with colonoscopy, but the odds of dying from colorectal cancer are lower for patients undergoing colonoscopy compared with patients not having a colonoscopy (SOR: B, based on extrapolation from a case-control study). Both strategies are cost-effective (SOR: A, based on a systematic review of high-quality cost-effective analyses). Bruce D. Boggs, MD, Mary M. Stephens, MD, MPH, Rick Wallace, MSLS East Tennessee State University, Johnson City