Abstract 5247: Aspirin use and estrogen receptor-negative breast cancer risk in African American women

Introduction: Use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of breast cancer; however, results of epidemiological studies have been mixed. Further, few previous studies investigated these associations among African American women and no studies that included African Americans evaluated whether associations differ by estrogen receptor (ER) status. Methods: To assess the relation of aspirin use to risk of ER+ and ER- breast cancer in African American women, we conducted a prospective analysis within the Black Women9s Health Study, an ongoing nationwide cohort of 59,000 black women that began in 1995. On baseline and biennial follow-up questionnaires, women reported regular aspirin use (defined as use at least three days per week) and years of use. Acetaminophen use was queried similarly. Among women with available information on aspirin use, 1701 invasive breast cancers occurred during follow-up through 2015, including 962 ER+ and 492 ER- tumors. All cancers were confirmed through pathology reports or state cancer registry data. We used age-stratified Cox proportional hazards regression models to estimate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for associations of aspirin use with risk of ER+ and ER- breast cancer. All models adjusted for age at menarche, oral contraceptive use, parity, age at first birth, estrogen plus progestin use, body mass index, alcohol consumption, and use of other NSAIDs. Results: Compared to never use, current regular use of aspirin was associated with lower risk of breast cancer overall (HR 0.87; 95% CI 0.76, 1.00). The association was driven by a statistically significant inverse association for ER- breast cancer (HR 0.76; 95% CI 0.58, 0.99); for ER+ breast cancer, the corresponding HR was 0.92 (95% CI 0.77, 1.09). In contrast, we found no associations with acetaminophen use. Conclusions: Our observation of reduced risk of ER- breast cancer in relation to current regular use of aspirin is consistent with anti-inflammatory effects of aspirin, rather than hormone-dependent pathways. Aspirin may represent a potential opportunity for chemoprevention of ER- breast cancer; however, these findings require corroboration in additional studies. Citation Format: Kimberly A. Bertrand, Traci N. Bethea, Hanna Gerlovin, Patricia Coogan, Lucile L. Adams-Campbell, Lynn Rosenberg, Julie R. Palmer. Aspirin use and estrogen receptor-negative breast cancer risk in African American women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5247.