Oral contraceptives and colorectal tumors. A review of epidemiologic studies.

Over the last two decades, the mortality rates of colorectal cancer in many developed countries have declined in women but not in men. One of the explanations of this difference between the genders may be the favorable influence of the spread of exogenous female hormone use (i.e., oral contraceptives [OC] and hormone replacement therapy) Reduced risk in ever-users of OC was found in three of four cohort studies available on this topic, and was significant in the one based on colorectal cancer mortality. The fourth one showed no difference. Of 11 case-control studies (or groups of studies), none showed significantly elevated risk. Five reported lowered colorectal cancer risk among ever-users, with a significant inverse association in the largest investigation available. Recent OC use, more than long duration use, seemed to be related to some risk reduction. One cohort study and three case-control investigations suggested that OC use was not related to the risk of colorectal adenomatous polyps. Thus, at present, it seems that OC use does not increase and may even have a favorable effect on either incidence or mortality of colorectal cancer.