In fact, a modest survival benefit was found in women who were moderate drinkers before and after diagnosis due to a reduced risk of dying from cardiovascular disease, a major cause of mortality among breast cancer survivors.
"Our findings should be reassuring to women who have breast cancer because their past experience consuming alcohol will not impact their survival after diagnosis," said Polly Newcomb, Ph.D., a member of the Public Health Sciences Division and head of the Cancer Prevention Program at Fred Hutchinson Cancer Research Center, who led the study.
"This study also provides additional support for the beneficial effect of moderate alcohol consumption with respect to cardiovascular disease."
The study was based on data from almost 23,000 women who participated in the Collaborative Breast Cancer Study, a National Cancer Institute-sponsored, multi-site, population-based study of risk factors for breast cancer. The study began in 1988 and was conducted in New Hampshire, Massachusetts and Wisconsin. In a smaller follow-up study between 1998 and 2001, about 5,000 participants were sent a follow-up questionnaire about their alcohol consumption habits after diagnosis.
Among study participants with a history of breast cancer, the authors found that the amount and type of alcohol a woman reported consuming in the years before her diagnosis was not associated with her likelihood from dying from breast cancer. However, the authors also found that those who consumed a moderate level of alcohol (three to six drinks per week) in the years before their cancer diagnosis were 15 percent less likely to die from cardiovascular disease than non-drinkers. Moderate wine consumption in particular was associated with a lower risk of cardiovascular disease mortality, while no such benefit was evident for consumption of beer or spirits, or for heavier levels of alcohol consumption.
Similar patterns were evident when considering reported alcohol consumption after breast cancer diagnosis. The amount and type of alcohol a woman consumed after diagnosis did not appear to be associated with survival of breast cancer, but those who consumed alcohol in moderation experienced a 39- to 50-percent lower mortality rate from cardiovascular disease.
Newcomb said that the difference in alcohol's impact on developing breast cancer risk and on survival from the disease could be that the kind of breast cancer that is more likely to be diagnosed among women who drink may be more responsive to hormone-reduction therapies.
Alcohol consumption is believed to influence breast cancer risk through increases in estrogen production in both pre- and post-menopausal women.
The study will be published in the Journal of Clinical Oncology.