The incidence of young-onset breast cancer (YOBC) is increasing, and is higher among Non-Hispanic Black (NHB) than Non-Hispanic White (NHW) women. While alcohol consumption is consistently linked to breast cancer risk, its role in YOBC specifically, is poorly understood. Moreover, it is unclear whether associations of alcohol and YOBC vary by tumor subtype or whether it contributes to disparities by race and/or socioeconomic position (SEP). We examined associations of lifetime alcohol use and YOBC overall and by tumor subtype, and assessed whether associations varied by race, and SEP. We hypothesized that alcohol consumption would be positively associated with YOBC risk, with stronger associations for estrogen receptor (ER)-positive subtypes and similar associations across race and SEP categories. Data are from the Young Women’s Health History study, a large population-based case-control study of breast cancer among NHB and NHW women < 50 years of age, from the Los Angeles and Detroit SEER registries. Controls (n=1,381) were identified through area-based sampling and frequency matched to invasive breast cancer cases (n=1,812) by age-group, study site and race. Lifetime average alcohol consumption was collected from in-person interviews, using life history calendars to facilitate accurate recall. Molecular subtypes were defined as: Luminal A (ER-positive and/or progesterone receptor (PR)-positive and human epidermal growth factor 2 (HER2)-negative with grades 1 or 2); luminal B (ER-positive and/or PR-positive and HER2-positive or ER-positive and/or PR-positive and HER2-negative with grade 3); HER2-type (ER-negative and/or PR-negative and HER2-positive); and triple negative (TN; negative for ER, PR, and HER2). Weighted multivariable logistic regression models, adjusted for established risk factors, were used to estimate odds ratios (OR) and 95% confidence intervals (CI) for associations of alcohol consumption and YOBC by subtype. Statistical interaction of alcohol by race and SEP was evaluated using the Wald’s test for the cross-product term. Women who consumed >20 g/day of alcohol were slightly leaner, less likely to have a college education and have a family history of breast cancer and more likely to have smoked than nondrinkers. Alcohol consumption was not significantly associated with YOBC risk overall, or within molecular subtype [LumA (>20 g/day vs. nondrinkers OR (95%CI) = 0.66 (0.43, 1.00), LumB=0.83 (0.53, 1.31), HER2=1.43 (0.63, 3.23), and TN=0.82 (0.52, 1.29)]. We did not observe any interaction by race (pint=0.62) or SEP (pint=0.94) overall or in models of tumor subtypes (all pint>0.28). Alcohol consumption of >20 g/day was inversely associated with LumA among NHW [OR (95%CI) =0.50 (0.28, 0.89)], however, no significant association was observed for LumA in NHB [OR (95%CI) =1.14 (0.61, 2.12)]. Our findings suggest that alcohol consumption is not strongly linked to YOBC risk, and that associations do not appear to vary by molecular subtype, race, or SEP.

Citation Format: Kelly A Hirko, Darek R Lucas, Dorothy R Pathak, Nicole Bohme Carnegie, Richard T Houang, Kendra Schwartz, Ellen M Velie. Alcohol consumption and risk of young-onset breast cancer among non-Hispanic Black and White women in the Young Women’s Health History Study [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C030.