Abstract
We present the outcomes of colorectal cancer screening conducted in cooperation with the Miyagi Cancer Society.
(1) Evaluation of effectiveness of colorectal cancer screening by the fecal occult blood test (FOBT): We evaluated the effectiveness of colorectal cancer screening by FOBT. As a result of a case-control study by the 2-day immunochemical fecal occult blood test (iFOBT) for colorectal cancer, the odds ratio of death from colorectal cancer for “the screened group within 2 years” versus the non-screened group was calculated as 0.50 (95CI: 0.27-0.94). The results suggested the effectiveness of the screening.
(2) FOBT accuracy: The sensitivity/false-negative rate of 2-day iFOBT was examined by the follow-up method based on the results obtained in 1993 and 1994 (H5 and H6). The numbers of true-positive cases and false-negative cases were 266 and 101, respectively. Accordingly, the sensitivity was calculated as 72.5%. However, when the cases diagnosed with colorectal cancer by screening were excluded from the false-negative group, the sensitivity was estimated as 89.6%. This result was regarded as satisfactory.
(3) Comparison of the work-up examination accuracy between SS + BE and TCS: As a result of sigmoidoscopy (SS) and barium enema (BE) recommended as the work-up examination at first, 436 colorectal cancer lesions were observed. The number of false-negative cases was 48. Accordingly, the sensitivity of SS + BE was found to be 90.1%. Twenty six (26) out of 48 cases were diagnosed when referred for treatment, and 19 out of 48 cases were diagnosed during follow-up examination. Several or more advanced cancer legions were found to have been missed in the right-sided colon because of failures in access by SS. In the case of TCS, there were no significant differences in the false-negative rate, while only few advanced colorectal cancers were found (that is to say, the miss rate of advanced colorectal cancers was extremely low). There were no differences in prognosis between the false-negative cases diagnosed when referred for treatment or during follow-up examination and the true-positive cases. However, prognosis was poor for cases diagnosed after the onset of clinical symptoms.
