Abstract
Mass screening examinations for colorectal cancer by occult blood testing of feces have been conducted for residents living in the Ota ward of Tokyo. Over a period of 25 years, a total of 225,851 residents have been examined, and 482 patients with colorectal cancer have been found. While the screening results were obtained by the qualitative method of the immune feces occult blood test (IFOBT), the complete examination (barium enema or colonoscopy) rate was about 50% and the cancer detection rate was 0.14%, both of which are low values. However, since 1998, when results began to be obtained by the quantitative IFOBT method, which evaluates the hemoglobin level in the feces, the complete examination rate and the cancer detection rate have been increasing annually.
Among the 89 patients in whom colorectal cancer was detected, 20 early-cancer cases and 11 advanced-cancer cases were from the group with quantitative IFOBT values of 500 ng/ml or less, and 8 early-cancer cases and 27 advanced cancer cases were from the group with quantitative IFOBT values of 2,000 ng/ml or higher. Thirty-two cases with colorectal cancer were found in the one-day IFOBT positive group and 57 cases were found in the two-day positive group; the colorectal-cancer detection rate and the advanced-cancer detection rate in the latter group were 1.8 times and 3.6 higher than those in the former group, respectively. Right colon cancer was detected in 2 cases of the one-day IFOBT positive group and 17 cases of the two-day positive group. The number of cases (72) in which cancer was detected in the group who had received yearly examinations in the previous years was less than the half of the 156 cases in which cancer was detected in the group who did not receive yearly examinations in the previous years. As for the problems of the screening, there were few new examinees, the complete examination rate was low, and medical accidents were overlooked. In order to address these problems, the mass-screening committee should analyze the annual screening results in detail and improve the accuracy control.
