According to a study published in the Journal of the National Cancer Institute, postmenopausal women who consume an average of 10 grams or more of alcohol per day are more likely than nondrinkers to develop estrogen receptor-positive breast cancer; there was no link between alcohol intake and estrogen receptor-negative breast cancer.
In the U.S.,10 grams of alcohol corresponds to less than one drink (a typical drink contains 12-14 grams of alcohol).
Alcohol intake is frequently reported to increase the risk of postmenopausal breast cancer, but it is uncertain whether the effect of alcohol on breast cancer risk varies by the estrogen receptor and progesterone receptor status of the breast tumor.
When breast cancers are diagnosed, these receptors are tested to determine whether the cancer is responsive to the female hormones estrogen and progesterone. The results provide information about prognosis and guide treatment decisions. Breast cancers may be positive for both receptors (ER+/PR+), negative for both receptors (ER-/PR-), or positive for only one receptor (ER+/PR- or ER-/PR+). A majority of breast cancers are estrogen-receptor positive.
The basis for a link between alcohol and breast cancer is not well understood, but may involve increased exposure to estrogen. If this is the case, alcohol may be linked with ER+ breast cancers, but not with those that are ER-. To evaluate whether the effect of alcohol intake on breast cancer risk varies by ER and PR status, researchers evaluated data from a Swedish mammography registry. Information about alcohol intake (as well as other exposures of interest) was collected by questionnaire from 51,847 postmenopausal women in 1987 and 1997. By June 2004, 1188 of these women had developed invasive breast cancer and had known ER and PR status.
The study found that the link between alcohol and breast cancer risk varied by ER status. Compared to non-drinkers, women who averaged 10 grams or more of alcohol per day were more likely to develop ER+ breast cancer (regardless of PR status), but were not more likely to develop ER- breast cancer. Among women who averaged 10 grams or more of alcohol per day, there were 232 cases of ER+ breast cancer per 100,000 women per year. The rate of ER+ breast cancer among nondrinkers was 158 cases per 100,000 women per year.
The study also suggested a possible interaction between alcohol and postmenopausal hormones: The link between alcohol and ER+PR+ breast cancer was stronger among women who had used postmenopausal hormones than among women who had never used postmenopausal hormones. The researchers caution, however, that they did not have information about the type or duration of use of postmenopausal hormones.
The researchers conclude that alcohol intake increases the risk of ER+, but not ER-, postmenopausal breast cancer. The link with ER+ breast cancer is noteworthy because the majority of postmenopausal breast cancers are ER+.
Reference: Suzuki R, Ye W, Rylander-Rudqvist T et al. Alcohol and Postmenopausal Breast Cancer Risk Defined by Estrogen and Progesterone Receptor Status: A Prospective Cohort Study. Journal of the National Cancer Institute. 2005;97:1601-8.