It is important to explore racial differences in mortality patterns due to breast cancer (BC), cardiovascular disease (CVD) and all-causes (AC) among women diagnosed with breast cancer in the U.S. Data from 891,635 non-Hispanic black (NHB) and white (NHW) women diagnosed with malignant breast cancer from 1990-2014 were obtained from the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database. Cumulative incidences for mortality due to BC and CVD were calculated at 2, 5, 10 and 20 years post-diagnosis by race and age (dichotomized at the study mean, 62.5 years). A Cox hazard model was used to obtain hazard ratios (HR) for all-cause mortality and the subdistribution hazards model was used for mortality due to BC and CVD, accounting for the presence of competing risks, along with their corresponding 95% confidence intervals (CI). A total of 300,445 deaths occurred over 6,319,054 person-years. Among women aged <62.5 years at diagnosis, the cumulative incidence of BC death and CVD death at 2, 5, 10, and 20 years was 5.2%, 10.6%, 15.3%, 19.5% and 0.2%, 0.6% 1.2%, 2.5%, respectively, for NHWs and 10.0%, 19.9%, 27.9%, 34.8% and 0.5%, 1.3%, 2.7%, 5.3% for NHBs. Results for BC were similar among women diagnosed >62.5 years, while there appeared to be no racial differences in CVD-death. Among women diagnosed at age <62.5 years, NHBs had an increased hazard of mortality due to BC (HR=2.03, 95% CI: 1.97, 2.08), CVD (HR=2.64, 95% CI: 2.38, 2.94), and AC (HR=2.84, 95% CI: 2.77, 2.91) during the first 2 years post-diagnosis. This association decreased over time for mortality due to BC (5-10 years: HR=1.76; 10-15 years: HR=1.58) and AC (5-10 years: HR=1.54; 10-15 years: HR=1.07, 15+ years: HR=0.93) but remained relatively stable for CVD (15+ years: HR=2.47). Among women diagnosed at age >62.5 years, NHBs had an increased hazard of mortality due to BC (HR=2.13, 95% CI: 2.06, 2.19), CVD (HR=1.33, 95% CI: 1.25, 1.40) and AC (HR=1.51, 1.48, 1.55) during the first 2 years post-diagnosis. The association decreased for BC (2-5 years: HR=1.55; 5-10 years: HR=1.15; 10-15 years: HR=0.88; 15+ years: HR=0.64) and CVD (2-5 years: HR=1.1.06; 5-10 years: HR=1.00; 10-15 years: HR=0.85; 15+ years: HR=0.65) while the association with AC mortality initially decreased, then remained relatively stable (5-10 years: HR=1.20). Results suggest NHB women diagnosed at younger ages have the highest cumulative incidence of mortality due to BC, CVD and AC over the 25-year follow-up period. In addition, among women diagnosed at younger ages, NHBs appeared to have a two-fold increase in hazards of AC, BC and CVD mortality during the years immediately following BC diagnosis compared to NHWs. The increased hazard for CVD mortality among younger NHBs remained relatively stable over time, whereas the hazards for AC and BC mortality attenuated over time. Results were less pronounced among women diagnosed at older ages.

Citation Format: Alyssa N. Troeschel, Yuan Liu, Lindsay Collin, Kevin Ward, Keerthi Gogineni, Lauren McCullough. Racial/ethnic differences in all-cause and cause-specific mortality patterns among a cohort of invasive U.S. breast cancer patients [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 4247.