Older women who drink alcohol are significantly more likely than nondrinkers to develop hormone-sensitive forms of breast cancer including lobular carcinoma and estrogen receptor-positive and progesterone receptor-positive tumors, according to an article in the October issue of Cancer Epidemiology, Biomarkers and Prevention.

Nearly 2,000 women from the same region, ages 65 to 79 years, were interviewed for the study; half had a history of breast cancer and half did not. Women with a history of breast cancer were identified through the population-based registry of cancer incidence maintained by a major cancer center.

Lead author Christopher I. Li, M.D., Ph.D., said "Women who were current drinkers who reported consuming at least 30 grams of alcohol a day - roughly the equivalent of two drinks - had an 80 percent higher risk of breast cancer compared to nondrinkers."
The American researchers found that risk varied by histologic type. "Current consumers of two or more drinks per day had more than three times the risk of lobular cancer (a 330 percent increased risk) and a 50 percent increased risk of ductal cancer," Li explained.

Although lobular breast cancer accounts for only 10 percent to 15 percent of all breast-cancer cases in the U.S., its incidence is on the rise. Earlier this year, the same research group reported a 65 percent increase in lobular cancer during the past decade, a trend that may be due to the increased use of combined estrogen and progestin hormone-replacement therapy. The incidence of ductal breast cancer, which accounts for about 80 percent of cases, has remained essentially constant during the same time frame.

Although lobular carcinoma can be somewhat more difficult to diagnose, tumors are more likely to be positive for estrogen and progesterone receptors. In the study, researchers found that current users of alcohol had a 40 percent increased risk of receptor-positive breast cancers.

"The marked increase in hormonally sensitive breast cancers, including lobular and estrogen receptor/progesterone receptor-positive tumors, among women who drink suggests a hormonal basis for the known association between alcohol use and breast-cancer incidence," Li said. "Alcohol is known to increase estrogen levels in the blood, and therefore it could stimulate hormonally sensitive tumors."

The researchers found no association between alcohol use and increased incidence of hormonally insensitive cancers.

Although alcohol use has been associated with a moderate increase in breast-cancer risk, few studies, until now, have stratified results by histology or hormone-receptor status, Li said. "This is one of the first studies to evaluate the relationship between alcohol use and breast cancer and how alcohol consumption modifies the risk of different types of breast cancer. While our results suggest that alcohol is strongly associated with hormonally responsive types of breast cancer, they need to be confirmed by other researchers."