Alcohol use is associated with breast cancer risk, with risk increasing by up to 10% for each drink per day. Much of this risk is thought to be hormonally driven, as alcohol metabolism increases estrogen levels in postmenopausal women. Because of this hypothesized mechanism, recent research has explored whether alcohol intake might differentially effect the risk for various molecular subtypes of breast cancer. As reported in Hormones and Cancer, Drs. Michelle Baglia and Christopher Li and colleagues in the Public Health Sciences Division found that the association of alcohol consumption with breast cancer risk varied by both histologic subtype and estrogen status of the tumor.
Breast cancer is actually a collection of diseases arising from normal breast tissue, with subtypes defined by histologic or hormonal characteristics. Histologically, roughly 70% of postmenopausal breast cancers in the United States are invasive ductal carcinomas (IDC), and 15-20% are invasive lobular carcinomas (ILC). Breast tumors are often additionally classified according to whether or not they express receptors for particular hormones, such as estrogen, and at least 90% of all ILC tumors are estrogen receptor positive (ER+). While previous studies suggest that alcohol use is more strongly associated with risk of lobular cancers than risk of ductal cancers, few studies have considered both histologic and hormonal factors simultaneously.
To evaluate risk from alcohol intake, the authors utilized data from a large population-based study of breast cancer in the greater Seattle area. From 2000-2008, women aged 55-74 diagnosed with a primary invasive breast cancer were identified through the Cancer Surveillance System and invited to participate in the study. In addition to 905 women with IDC, 567 with ILC, and 489 with invasive ductal-lobular carcinoma (IDLC), 891 women without breast cancer agreed to participate as controls. In-person structured interviews were used to collect information on myriad lifestyle factors including alcohol intake. Importantly, the researchers collected information about not only total current alcohol intake, but also type of alcohol intake (beer, white wine, red wine, liquor). Polytomous regression was used to evaluate the association between current alcohol intake, overall and by drink type, with combinations of histologic subtype and ER status.
By histology, the authors found a dose-response relationship between the average number of drinks per week and risk of ILC, with a 52% higher risk among those drinking at least 7 drinks per week compared to never drinkers. When considering the type of alcohol, drinking at least 4 drinks of liquor per week was significantly associated with risk of both ILC and IDC, but not IDLC. Stratifying by ER status, the positive association of alcohol intake with ILC remained statistically significant for ER+ ILC cases. Among IDC cases, alcohol consumption was associated with increased risk of ER+ IDC, but decreased risk of ER- IDC. No associations were observed among ER+ IDLC cases.
Overall, these findings contribute to the growing etiological understanding of breast cancer. Said lead author Dr. Baglia, “while alcohol consumption has previously been shown to increase risk of breast cancer, our study further suggests that this association differs by subtype of breast cancer. This offers some additional understanding of the differences in risk for different types of breast cancer. By better understanding the different risk factor profiles of different subtypes of breast cancer, breast cancer prevention can be personalized to individuals.”
Also contributing to this project from the Fred Hutch were Drs. Kathleen Malone and Mei-Tzu Tang.
Baglia ML, Malone KE, Tang MC, Li CI. Alcohol Intake and Risk of Breast Cancer by Histologic Subtype and Estrogen Receptor Status Among Women Aged 55 to 74 Years. Horm Cancer 2017; doi: 10.1007/s12672-017-0297-2.
Funding for this study was provided by the National Cancer Institute (NIH) and the Department of Defense.