Epidemiologic findings regarding the relation between alcohol consumption and risk of breast cancer have been inconsistent. We performed a meta-analysis (a quantitative review) of the available data. To evaluate whether there was a dose-response relation between alcohol consumption and risk of breast cancer, we fitted mathematical models to the pooled data. There was strong evidence to support a dose-response relation in both the case-control and follow-up epidemiologic data. Using the dose-response curves that we calculated, the risk of breast cancer at an alcohol intake of 24 g (1 oz) of absolute alcohol daily (about two drinks daily) relative to nondrinkers was 1.4 (95% confidence interval, 1.0 to 1.8) in the case-control data and was 1.7 (95% confidence interval, 1.4 to 2.2) in the follow-up data. We interpret these findings not as proof of causality, but as strongly supportive of an association between alcohol consumption and risk of breast cancer.
Longnecker MP, Berlin JA, Orza MJ, Chalmers TC. A Meta-analysis of Alcohol Consumption in Relation to Risk of Breast Cancer. JAMA. 1988;260(5):652-656. doi:10.1001/jama.1988.03410050072032