As announced in November 2011, a 30-year study of 100,000 women being published in the Journal of the American Medical Association finds that consuming even small amounts of alcohol increases the chance of breast cancer, with an average of two glasses daily raising the disease risk by 51%.

http://www.france24.com/en/20111101-even-light-drinkers-increase-breast-cancer-risk-study,
http://www.boston.com/lifestyle/health/articles/2011/11/02/light_drinking_may_raise_breast_cancer_risk/