Screening for colorectal cancer

PURPOSE: Screening for colorectal cancer using a guaiac-based fecal occult blood, or Hemoccult, test has been demonstrated to reduce colorectal cancer mortality. However, the magnitude of effectiveness is relatively low because of poor sensitivity of the Hemoccult test. The immunochemical fecal occult blood test has been shown to be much more sensitive than the Hemoccult test in detecting preclinical colorectal cancer in an asymptomatic population. The purpose of this article is to discuss the validity of the immunochemical fecal occult blood test and the efficacy of a population-based screening program using the test. METHODS: Relevant articles were primarily identified through MEDLINE search. Review was focused on the studies of population screening programs with the immunochemical fecal occult blood test. RESULTS: Sensitivities for colorectal cancer calculated in the same population were reported to be 67 to 89 percent and only 33 to 37 percent for the immunochemical test and Hemoccult test, respectively. Case-control studies and other observational studies showed that screening programs using the immunochemical fecal occult blood test by hemagglutination reaction would reduce the risk of dying of colorectal cancer by 60 percent or more for those screened annually compared with those unscreened. It was also shown that a screening strategy using the immunochemical fecal occult blood test had the best cost-effectiveness ratio among the methods available. Nearly 5 million persons are currently screened per year in Japan, yielding 0.15 to 0.2 percent colorectal cancer cases among persons with positive fecal occult blood test results. CONCLUSIONS: These results strongly suggest that a screening program with immunochemical fecal occult blood test has promising advantages in terms of effectiveness over programs with the Hemoccult test. More stress is warranted on introduction of immunochemical fecal occult blood testing as a screening test in place of the guaiac fecal occult blood test.