Consuming as few as 3 to 4 drinks a week can increase the risk, researchers say.
A study of 1,897 women with early-stage breast cancer, the Life After Cancer Epidemiology study, found for even light drinkers there was an an increase in risk of breast cancer recurrence and breast cancer death, but no effect on total mortality.
Why does alcohol affect your risk for breast cancer? According to About.com Breast Cancer Guide Pam Stephan, "Estrogen is a hormone that fuels 80% of all cases of breast cancer. Any kind of alcohol that you consume may change the levels of female hormones, and thus cause more cases of estrogen-receptor positive breast cancer."
No Level of Drinking Safe
Stephen also said there is no level of alcohol consumption that is safe.
"For women, one drink of an alcoholic drink per day raises your risk very slightly. Your risk of developing breast cancer goes up to 10% if you have two drinks a day. If you consume three drinks daily, your risk rises to 30%," she said.
The LACE study also indicated that alcohol was an even greater risk for women who were postmenopausal and overweight.
Source: M Kwan, et. al. "Alcohol Consumption and Breast Cancer Recurrence and Survival among Women with Early-Stage Breast Cancer," Thirty-Second Annual CTRC-AACR San Antonio Breast Cancer Symposium-- Dec 10-13, 2009; San Antonio, TX.