[Mass surveys for detection of colorectal cancer].

In Japan, an immunochemical fecal occult test is the first step in mass surveys for detection of a colorectal cancer. A person with false-negative fecal occult blood has early cancer and/or cancer less than 3 cm in diameter. If the end of the mass survey is mp cancer (cancer involvement to the colonic wall), the false-negative rate for colorectal cancer is less than 10%. A person with a positive reaction on the fecal occult test is taken forward to the second step. The second step in the mass survey consists of barium enema or/and endoscopy. Endoscopic false-negative cancers are located behind the physical flexure section or the colonic haustra. Radiologic false-negative cancers are type II cancer or cancer less than 1 cm in diameter or on the right side of the colon. In our experience, we have rarely overlooked cancer more than 2.1 cm in diameter by colonoscopy or barium enema. Most mp cancers are more than 2 cm in diameter. Thus, with colonoscopy or radiology we overlooks less than 10% of mp cancer.