Racial inequities in second-line treatment and overall survival among patients with metastatic breast cancer.

BACKGROUND: Black women in the USA have a higher incidence and mortality of metastatic breast cancer (mBC) than White women, while Hispanic women have lower rates. Previous studies have focused on first-line (1L) treatment, but little is known about racial differences in treatment beyond 1L and their impact on outcomes. METHODS: This analysis utilized data from an electronic health record derived de-identified database and included patients with HR+HER2- mBC initiating 2L treatment (including CDK4/6-inhibitor [CDKi]-based, endocrine monotherapy, everolimus combination therapy, and chemotherapy and other systemic therapies) between 2/3/2015 and 7/31/2021. Real-world overall survival (rwOS) was defined as time from 2L initiation to death. Multinomial logistic regression assessed the likelihood of 2L treatment between race/ethnicity groups. Median rwOS was estimated using the Kaplan-Meier method and adjusted hazard ratios were estimated using multivariable Cox proportional hazards models. RESULTS: Among all patients who received 2L, non-Hispanic Black (NHB) and Hispanic/Latino patients were less likely to receive 2L CDKi compared to non-Hispanic White (NHW) patients (36%, 39% vs 42%, respectively). Median rwOS was 20.4, 37.6, and 25.3 months, in NHB, Hispanic/Latino and NHW patients, respectively. The rwOS remained poorer among NHB patients after adjustment (HR = 1.16; p = 0.009). In stratified analysis, adjusted rwOS was similar between NHB and NHW patients among those who received 1L CDKi. CONCLUSIONS: These findings suggest that among patients with HR+HER2- mBC, NHB patients had worse survival beyond front-line setting, mainly among the subset of women who did not receive CDKi at 1L. This inequities in rwOS between race/ethnicity groups was not observed among patients who received 1L CDKi.