[Multiple tumors of colon and rectum].

The possible occurrence of multiple synchronous or metachronous malignant lesions in patients with carcinoma of the colon and rectum is a well known event. In this population-based study in the Geneva area from 1970 to 1986, the frequency of synchronous colorectal carcinomas was 1.1% and that of metachronous carcinomas 1%. The relative risk of metachronous colorectal carcinoma is higher than in the general population (colon after rectum 1.2, colon after colon 1.7 and rectum after rectum 1.4). A high association of adenomatous polyps with multiple colorectal carcinoma was observed. The 5-year actuarial survival in case of curative resection was 87% for metachronous carcinomas, 35% for single carcinomas and 33% for synchronous carcinomas. We conclude that complete preoperative colonoscopy, whenever possible, should be performed to screen patients with synchronous carcinomas. Finally, a lifelong follow-up of the residual colon or rectum should be planned to detect metachronous lesions.