Relationship between breast cancer and colorectal adenomatous polyps. A case-control study.

Although there is a known reciprocal association between breast and colorectal cancer in women, few studies have investigated whether a similar association exists between breast cancer and colorectal adenomatous polyps, known to be precursor lesions for colon cancer. A case-control study was conducted on patients in three colonoscopy practices in New York to determine possible risk factors for adenomatous polyps. Among women studied, there were 128 patients with incident adenomatous polyps and 284 control subjects who underwent colonoscopy and had no colorectal neoplasia. No significant association between the incidence of an adenomatous polyp in the colon or rectum and a history of breast cancer was found (odds ratio, 0.71; 95% confidence interval, 0.34 to 1.64). If shared risk factors for breast and colorectal cancer are the reasons for the concurrence of these two malignant lesions, these results suggest that these factors act at the level of promoting adenomatous polyps of the colon and rectum into colorectal cancer.