Parity and colorectal cancer risk in women.

A case-control study is reported of reproductive history and colorectal cancer risk based on information obtained from interviews with white women 40--79 years old who were admitted to Roswell Park Memorial Institute between the years 1957 and 1965. Women with the primary diagnosis of carcinoma of the colon (n = 284) and carcinoma of the rectum (n = 270) did not differ significantly in their prior reproductive histories as compared to those of a control group of women (n = 1,763) with nonneoplastic diseases not affecting the breast or reproductive sites. The peritinent literature suggesting a parity--colorectal cancer association in women is reviewed. The conclusion reached is that the evidence for a parity-colorectal cancer association is equivocal; but that if such an association exists, it is probably weaker than that seen for cancers of the breast, ovary, and uterine corpus.