Six-year results of annual colonoscopy after resection of colorectal cancer.

Colonoscopy is an important diagnostic and therapeutic tool that may also be useful in the surveillance of patients after curative resection of colorectal cancer. The yield of colonoscopy and the frequency with which it should be performed after operation, however, have not been clearly defined. Over the past 10 years, we have examined these patients annually with colonoscopy or barium enema. This study evaluates the results of a specifically designed protocol that followed 174 patients. Counting all sites, colorectal cancer recurred in 57 of 174 patients, three-quarters within the first 24 months. Nine anastomotic recurrences were detected in the 12-30 month interval; none was reoperated for cure; however, 4 metachronous colon cancers were found and resected for cure. In addition, 30 polyps larger than 1 cm in size and 7 villous adenomas were removed in 30 patients. Combined, these findings represent an interval yield of 3-5% per year. Based on these results and other reports, we recommend that patients undergo colonoscopy annually at least for the first 6 years postresection of colorectal cancer. The detection of new primary tumors and possibly predisposing lesions becomes more important in these patients than detection and cure of recurrent disease.