[Familial occurrence of cancer of the colon and the rectum: results of a 3-year case-control survey].

A case-control study of the familial prevalence (first-degree relatives) of colorectal carcinoma (CRC) was performed from October 1979 through March 1983 in: (a) 170 consecutive patients with histologically proved rectal (n = 64) or colonic (n = 106) adenocarcinoma; cases of familial polyposis coli and cancer family syndrome were systematically excluded from the study; (b) 170 control subjects, who were free of CRC or colorectal adenoma(s) and matched to patients according to sex and age; (c) 170 consecutive patients with common rectal or colonic adenoma(s), and no evidence of polyposis coli; (d) 100 patients with cancer of various organs, excluding CRC and primary tumours known to be epidemiologically related to CRC. Results of family studies were expressed as "proved" (when the pathological report was received) or "probable" CRC. Eighteen (10.6 p. 100) of the 170 patients with CRC had at least one first-degree relative with past or present proved CRC, and 14 (8.2 p. 100) with probable CRC; the corresponding figures were 3 (1.7 p. 100) proved and 3 (1.7 p. 100) probable CRC in the control group, 14 (8.2 p. 100) proved and 11 (6.5 p. 100) probable CRC in the "adenoma" group and 1 (1 p. 100) and 3 (3 p. 100) in the non-colonic carcinoma group. The relative risk of CRC in close relatives was 6.3 and 4.7 in the CRC and adenoma groups respectively. For the variables studied no significant differences were found between males and females.(ABSTRACT TRUNCATED AT 250 WORDS)