Abstract
Since 1983 to 1987, five hundred forty-eight patients with colorectal adenoma were diagnosed in our mass screening program for colorectal cancer. We have used flexible sigmoidoscopy and double contrast barium enema as the work-up strategy for the cases of positive fecal occult blood test (FOBT). And we have also use the same work-up examina-tion as the surveillance after endoscopic treatment for colorectal adenoma. The 1st and 2nd surveillances after initial treatment were performed in 507 and 385 cases, out of 548, respectively. The detection rate of the other adenoma in the surveillances was about 40%, and this proportion was common to twice surveillances, but detection of new cancer were rare, only 5 cancers were diagnosed in our series. From present study, the risk factors of diagnosed as carrying the other adenoma at the 1st surveillance were identified "multiple adenomas" with odds ratio of 3.0 and "male" with odds ratio of 2.2, but was not "age at the initial treatment". Using the data of three time examinations in the 385 patients, we derived the sensitiv-ity of work-up examination and the rate of newly developing adenoma. With limitation of larger than 5mm in diameter, the sensitivity of work-up examination for adenoma was 84% in entire colon, and was 92% in rectum and sigmoid colon. But with same limitation, the rate of newly developing adenoma was 0.02/person-year in entire colon and was 0.006 in rectum and sigmoid colon. With the use of both flexible sigmoidoscopy and barium enema, it was considered that undiagnosed diminutive adenomas still remained, but newly developing large adenomas were very rare. Consequentry, other less expensive follow-up programs, for example FOBT, should be applied in the patients after colorectal polypectomy, and the intervals of surveillance by work-up examination can be prolonged.
