Background: Although black and white women have a similar incidence of breast cancer, black women have a higher breast cancer mortality rate. The mortality is due, in part, to differences in tumor subtypes. Compared with white women, black women are more often diagnosed with aggressive tumors that have a poor prognosis, such as triple-negative breast cancer (TNBC). Among women diagnosed with TNBC, some studies have noted that survival is worse for black women as compared to white women. However, other studies have failed to identify any differences. The present study will leverage a large national hospital-based cancer registry to evaluate all-cause mortality differences, overall and by stage, in this high-risk population of breast cancer patients.

Methods: This study is a retrospective analysis of patients with breast cancer diagnosed between 2010 and 2014 who were included in the National Cancer Data Base (NCDB). Sponsored by the Commission on Cancer of the American College of Surgeons and the American Cancer Society, the NCDB is a nationwide cancer database that captures approximately 70% of all newly diagnosed cancers in the United States from approximately 1,500 hospitals accredited by the Commission on Cancer. Patients were included if they were non-Latina (nL) black or nL white and were diagnosed with stage I-IV tumors. Cox proportional hazards regression was used to estimate hazard ratios (HR) and corresponding associated 95% confidence intervals (CI). The baseline model adjusted for age and comorbidity. Additional models sequentially adjusted for tumor characteristics, treatment receipt, environmental factors (e.g., urbanicity), and then hospital facility characteristics (e.g., cancer program type). All models were stratified by stage.

Results: A total of 15,796 nL black and 51,643 nL white patients were identified. Baseline models showed that among all (stages) women with TNBC, black women had a 23% higher risk of mortality as compared to white women (HR=1.23; 95% CI: 1.19-1.28). However, these racial/ethnic differences were eliminated after adjusting for tumor characteristics (including stage) and treatment receipt. Stratified baseline models revealed that racial/ethnic disparities were limited to women with Stage I ((HR=1.16; 95% CI: 1.05-1.27) or Stage III cancers (HR=1.12; 95% CI: 1.04-1.20). After accounting for differences in tumor characteristics and treatment, the disparities were erased. Among women with Stage II and IV TNBC, no racial/ethnic differences in survival were noted in the baseline models or in any of the adjusted models.

Conclusion: Black/White disparities in all-cause mortality among women with TNBC varied by stage at diagnosis. Differences in tumor characteristics and treatment helped explain the disparity among those with Stage I or III cancers. More equitable access to treatment could help ameliorate mortality disparities among women with TNBC.

Citation Format: Adrienne Cobb, Abigail Silva, Shelly Lo, Alexandrina Balanean. Assessment of black/white differences in all-cause mortality among patients with triple-negative breast cancer [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C099.