April 14, 2008 (San Diego) -- Even a drink or two a day of alcohol may raise
the risk of the most common type of breast tumors -- those fueled by the
hormones estrogen and progesterone, according to one of the largest studies if
A second study shows that specific variations within two genes involved in
metabolizing alcohol are associated with an increased risk for breast cancer in postmenopausal
While the studies do not prove cause and effect, they lend plausibility to
growing evidence implicating drinking as a risk factor for breast cancer, says Elizabeth Platz,
ScD, a specialist in cancer prevention at the Johns Hopkins Bloomberg School of
"The beauty of the research is that it tells us something about the
mechanisms" by which alcohol may raise breast
cancer risks, she tells WebMD.
Platz moderated a news conference to discuss the findings at the annual
meeting of the American Association for Cancer Research.
Alcohol and Breast Cancer Risk
Some breast tumors are fueled by hormones, while others are not. In the
first study, National Cancer Institute (NCI) researchers wanted to determine if
the hormone status of a tumor influences the relationship between alcohol use
and breast cancer risk.
The researchers reviewed data on 184,418 postmenopausal women, who answered
questions about how much alcohol and what type of alcohol they drank each day.
They were followed for an average of seven years.
Overall, moderate drinking raised the risk of developing breast cancer,
regardless of whether a woman's preference was for beer, wine, or hard liquor.
And the more she drank, the greater the risk.
But most of the increased risk was seen in women whose tumors were fueled by
both estrogen and progesterone, says Jasmine Q. Lew, a fourth-year medical
student at the University of Chicago who led the research.
These tumors, referred to by doctors as being estrogen-receptor and
progesterone-receptor positive, or ER+/PR+, account for many breast
Compared with teetotalers, women who drank one to two drinks a day were 32%
more likely to develop ER+/PR+ breast cancer. Having three or more drinks daily
raised the risk of ER+/PR+ tumors by 51%.
Lew says that drinking alcohol also appeared to raise the risk of a more
aggressive type of tumor known as estrogen-receptor positive,
progesterone-receptor negative, or ER+/PR-. But so few women fell into this
category that the finding could have been due to chance.
In women with estrogen-receptor negative, progesterone-receptor negative
(ER-/PR-) tumors, there did not appear to be a link between drinking and breast
Why would drinking raise the risk of hormone-fueled tumors? "Our
hypothesis is that alcohol interferes with estrogen metabolism, which in turn
increases the risk of hormone-sensitive breast cancer," Lew tells