Abstract B123: Understanding racial disparities in breast cancer mortality beyond 10 years: The role of estrogen receptor status

Abstract Background: Despite improvements in breast cancer mortality, the risk of recurrence is high—approximately 20–40% and persisting decades after the initial diagnosis. Late recurrences—10 years or more after the primary diagnosis—are limitedly understood at the population level. Cancer registries do not routinely report recurrences; however, among women diagnosed with non-metastatic breast cancer and treated with curative intent, a recurrence is a necessary condition preceding death due to breast cancer. Racial disparities in breast cancer mortality have primarily focused on the first 5–10 years after diagnosis. We used data from the Surveillance Epidemiology and End Results cancer registry system to examine racial disparities in late breast cancer mortality to provide an initial look at potential disparities in late recurrence. Methods: We included women aged ≥20 years, diagnosed with stage I–III first primary breast cancer and self-reported race and ethnicity of non-Hispanic Black (NHB) or non-Hispanic White (NHW) between 2000 and 2011. The total cohort included all diagnoses, and the long-term survivors restricted the total cohort to women who survived 10 years or more. We estimated cumulative incidence of late breast cancer mortality by race and tumor characteristics. Cox proportional hazards regression was used to calculate age-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) in the total and long-term survivor cohorts, overall and by race. Results: Among the 338,964 breast cancer patients identified with stage I–III breast cancer in the SEER database, 237,238 (70%) survived 10 or more years after diagnosis. The median follow-up for the long-term survivors was 14.8 years (IQR: 12.6, 17.8). The long-term survivors were, on average, younger at diagnosis (58 years vs 68 years), more likely to be married (61% vs 41%), have a low-grade tumor (22% vs 14%), estrogen receptor (ER)-positive breast cancer (74% vs 64%), and localized breast cancer stage (69% vs 46%). The long-term survivors included 25,292 (11%) NHB and 211,946 (89%) NHW patients. In the overall cohort, NHB women were 1.85 times more likely to die from breast cancer compared with NHW women (95%CI: 1.81, 1.89), which was attenuated but persisted among long-term survivors (HR=1.33, 95%CI: 1.26, 1.41). Those with ER− tumors had higher mortality rates than ER+ in the overall cohort (HR=1.88, 95%CI: 1.84, 1.91); however, this association flipped in the long-term survivor cohort (HR=0.59, 95%CI=0.55, 0.63). Notably, NHB women with ER+ tumors had the highest cumulative incidence of late breast cancer mortality (9.6%) followed by NHW ER+ (7.3%), NHB ER− (5.3%), NHW ER− (4.1%). Conclusions: Our preliminary results suggest that deaths due to breast cancer occurring 10 or more years after diagnosis are largely driven by ER+ tumors. These deaths differentially impact NHB patients, suggesting that late recurrence risk may differ. Further exploration of the factors contributing to these disparities in outcomes among ER+ tumors may be warranted to achieve health equity. Citation Format: Lindsay J. Collin, Maret L. Maliniak, Jeffrey M. Switchenko, Lauren E. McCullough. Understanding racial disparities in breast cancer mortality beyond 10 years: The role of estrogen receptor status [abstract]. In: Proceedings of the 18th AACR Conference on the Science of Cancer Health Disparities; 2025 Sep 18-21; Baltimore, MD. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2025;34(9 Suppl):Abstract nr B123.