The researchers report that even moderate alcohol consumption -- defined as one or two drinks per day -- increased risk of developing ERplus/PRplus cancer -- positive for both the estrogen and progesterone receptors and the most common type of breast cancer -- and the more a woman drank, the higher her risk, the study's first author Jasmine Q. Lew, a fourth-year medical student at the University of Chicago, said.

Tumor hormone receptor status correlates with overall survival in metastatic breast cancer;

however, the influence of hormone receptors on the pattern of disease spread is not well known.

The study found that compared to women who did not drink at all, women who had three or more glasses of alcohol daily had as much as a 51 percent increased risk of ER+/PR+ breast cancer.

"This suggests that a woman should evaluate consumption of alcohol along with other known breast cancer risk factors, such as use of hormone replacement therapy," Lew said in a statement.

The finding was presented at the American Association for Cancer Research 2008 annual meeting in San Diego.