Alcohol consumption and breast cancer.

Epidemiologic studies of the relationship of alcohol consumption and breast cancer are generally in support of a direct association, although they are not entirely consistent. Studies supporting this finding have come from many countries around the world and from many investigators working with different study designs and types of populations. Ten of 16 case-control studies, and five of six cohort studies have produced results supporting a positive association. When evaluated together through techniques such as meta-analysis, these studies suggest that there is a 50% increase in breast cancer risk for women who average between one and two drinks per day. All types of alcoholic beverages seem to increase the risk, but there is little agreement between studies on dose-response relationships. No biologic explanation for alcohol's possible role in breast carcinogenesis is yet known, but several hypotheses have been advanced. In the absence of any effective method of primary breast cancer prevention, and because current risk factors explain so little of the incidence of this common cancer, alcohol consumption is of potential importance from both public health and etiologic perspectives. The possible protective effect of moderate alcohol consumption on heart disease should be considered when assessing the risks of this level of consumption on breast cancer.