A large new prospective study has reported that alcohol use may be more strongly associated with the risk of hormone-sensitive breast cancers than hormone-insensitive subtypes, especially hormone receptive positive lobular breast cancer. The study was designed to evaluate how alcohol-related risk varies by breast cancer subtype among postmenopausal women. Alcohol intake is a well-established risk factor for breast cancer. The study included 87,724 participants in the Women's Health Initiative Observational Study prospective cohort from 1993 to 1998 who reported their own alcohol consumption. A total of 2,944 invasive breast cancers were diagnosed among the participants during the follow-up period, which lasted until September 15, 2005.

Alcohol consumption was found to be associated with increased risk of invasive breast cancer overall. When risk by breast cancer subtype was examined, alcohol was associated with increased risk of lobular breast cancer and hormone receptor-positive (ER+/PR+) tumors. Women who consumed seven or more alcoholic beverages per week had almost twice the risk of hormone receptor-positive lobular breast cancer than nondrinkers. Women who had seven or more drinks per week also had a slightly increased risk of ductal breast cancer, but this association was not statistically significant. The absolute rate of hormone receptor-positive lobular cancer among current drinkers was 8.5 per 10,000 person-years compared to 5.2 for never drinkers, a level that was 63% higher. On the other hand, for hormone receptor-positive ductal breast cancer, the rates were 17.9 and 15.2 per 10,000 person-years, an 18% difference. (Note that the higher overall rates of ductal breast cancer compared to lobular breast cancer were expected since lobular breast cancer is a less common type.) The authors conclude that alcohol use may be more strongly associated with the risk of hormone-sensitive breast cancers than hormone-insensitive subtypes such as triple negative disease, suggesting distinct pathways for the development of these two subtypes.