Colonoscopic screening examination of relatives of patients with colorectal cancer. II. Relations between tumour characteristics and the presence of polyps.

Colonoscopy was offered to 206 first-degree relatives of 181 patients operated on for colorectal cancer (CRC). Findings of polyps in relatives correlated with Dukes staging, extent of dedifferentiation and localization of tumour in the operated patient, and type of family relationship. Adenomas in relatives and Dukes staging of carcinoma in the patients were inversely related. Relatives of patients with Dukes stage A tumour had more than twice as many adenomas as and a higher prevalence of multiple adenomas than relatives of patients with advanced cancer at the time of operation. If the patient had polyp(s) in addition to tumour, the number of adenomas per relative was almost doubled. Hyperplastic polyps in relatives were associated with poorly differentiated carcinoma in their related patients. These results support the theory that not all CRC are derived from polyps and that adenoma-derived CRC may have a better prognosis than 'de novo' CRC. An adenoma prevalence risk table is also presented.