New Data on Alcohol and Breast Cancer Show Link Is Complex

Alcohol consumption is a risk factor for breast cancer, according to several studies in recent years. But the scientific community confronts many unanswered questions on exactly how and why, and whether the amount and frequency of consumption or the type of beverage plays a role.

Two new studies add to the debate. One finds that drinking is not a risk factor for the most common form of breast cancer, but does heighten the risk of a less common form. The other study finds that for women with a specific genetic risk for breast cancer, wine may actually reduce the risk.

The first study was conducted by Dr. Christopher Li and colleagues at the Fred Hutchinson Cancer Research Center in Seattle and was published online in the Journal of the National Cancer Institute. Li and colleagues collected data on women enrolled in a larger study, the Women's Health Initiative, who reported their history of alcohol use and were tracked from 1993 to 2005.

The team grouped the women into six categories according to the average number of drinks per week, starting from less than one drink per week to more than 14 drinks per week. They then compared the type of breast cancer versus alcohol consumption.

The researchers found that women who consumed seven or more drinks weekly—compared to those who abstained—suffered a higher risk of lobular carcinoma, a form of cancer that develops in the milk production area of the breast. But they did not suffer a significantly higher risk of the more prevalent form of cancer—ductal carcinoma, which develops in the tubes that carry milk. Ductal cancer accounts for about 70 percent of all breast cancer cases, whereas lobular cancer accounts for about 10 to 15 percent of cases.

"We found that women who drank one or more drinks per day had about double the risk of lobular type breast cancer [compared to nondrinkers], but no increase in their risk of ductal type breast cancer," the study reads. The authors argue that the research suggests the two types of breast cancer have different pathways and more study is needed.

The second study, conducted by several researchers in Ottawa as part of the larger Hereditary Breast Cancer Clinical Study Group, was published June 11 in Breast. The team focused on the link between alcohol and breast cancer in women with two specific gene mutations that raise the risk of cancer. BRCA1 and BRCA2 are human genes that are known as tumor suppressors. Women born with mutations in one of these genes have a higher risk of breast and ovarian cancers.

For the study, 54 medical centers in eight countries contributed data. Scientists at the University of Ottawa's department of epidemiology and community medicine coordinated and analyzed the information. They compared data on women with one of the two mutations who developed invasive breast cancer to women with the same mutation who had not developed breast cancer. The scientists compared the rates of cancer to alcohol consumption, breaking it down by beverage preference.

The authors found a possible reduction in the risk of breast cancer for women with the BRCA1 mutation who drank moderately, but not for women with the BRCA2 mutation. Furthermore, the reduction in risk was only for wine consumers, who had an 18 percent lower risk than nondrinkers.

"While one should not overinterpret epidemiologic data in the absence of identified biological mechanisms," the text states, "there have been a very large number of experimental studies showing that certain polyphenols present in wine actively impede the initiation and growth of cancer cells."