REDUCING MORTALITY FROM COLORECTAL-CANCER BY SCREENING FOR FECAL OCCULT BLOOD

Background. Although tests for occult blood in the feces are widely us ed to screen for colorectal cancers, there is no conclusive evidence t hat they reduce mortality from this cause. We evaluated a fecal occult -blood test in a randomized trial and documented its effectiveness. Me thods. We randomly assigned 46,551 participants 50 to 80 years of age to screening for colorectal cancer once a year, to screening every two years, or to a control group. Participants who were screened submitte d six guaiac-impregnated paper slides with two smears from each of thr ee consecutive stools. About 83 percent of the slides were rehydrated. Participants who tested positive underwent a diagnostic evaluation th at included colonoscopy. Vital status was ascertained for all particip ants over 13 years of follow-up. A committee determined causes of deat h. A single pathologist determined the stage of cancer for each tissue specimen. Differences in mortality from colorectal cancer, the primar y study end point, were monitored with the sequential log-rank statist ic. Results. The 13-year cumulative mortality per 1000 from colorectal cancer was 5.88 in the annually screened group (95 percent confidence interval, 4.61 to 7.15), 8.33 in the biennially screened group (95 pe rcent confidence interval, 6.82 to 9.84), and 8.83 in the control grou p (95 percent confidence interval, 7.26 to 10.40). The rate in the ann ually screened group, but not in the biennially screened group, was si gnificantly lower than that in the control group. Reduced mortality in the annually screened group was accompanied by improved survival in t hose with colorectal cancer and a shift to detection at an earlier sta ge of cancer. Conclusions. Annual fecal occult-blood testing with rehy dration of the samples decreased the 13-year cumulative mortality from colorectal cancer by 33 percent.