133 Racial Disparities in Biomarker Testing, Treatment Utilization, and Outcomes in Patients with Metastatic Triple-Negative Breast Cancer (mTNBC) in U.S. Community Practices

Background

Although therapeutic advances have improved outcomes in metastatic triple-negative breast cancer (mTNBC), racial disparities in biomarker testing and access to modern treatments may influence overall survival (OS). This study describes rates of biomarker testing, treatment patterns, and OS by racial group among patients managed in US community oncology practices.

Materials and Methods

We retrospectively evaluated data from 450 adult patients with mTNBC (White, n = 270; Black, n = 105; Hispanic, n = 45; other minorities, n = 30) across 25 community oncology centers within the ONCare Alliance Network. Eligible patients were diagnosed with mTNBC from January 1, 2018, through December 31, 2023; were an age greater than or equal to 18 years; and did not receive therapy in an interventional clinical trial in the mTNBC setting. Data were collected from diagnosis of mTNBC until death or completion of up to 3 lines of systemic therapy. Data collected included demographics, comorbidities, ECOG performance status, hematologic indices, treatment regimens, and key actionable biomarkers. Six-month and 12-month OS were estimated using the Kaplan-Meier method for each racial group.

Results

Across cohorts, the mean age was 61 years (SD, 14), and the median Charlson Comorbidity Index score was 6 (IQR, 6-11). Across all groups, 76.2% and 78.0% of patients were tested for PD-L1 expression and for BRCA1/2 mutations, respectively. More Hispanic (93.3%) patients received systemic therapy than White (83.7%), Black (81.0%), and other minorities (76.7%) patients. Hispanic patients also had the highest probability of survival at 12 months and longest median OS (Table).

Conclusions

This real-world study revealed that high rates of guideline-recommended biomarker testing and timely treatment initiation can be achieved across racial groups. Encouragingly, outcomes between Black and White patients also suggested that coordinated community oncology networks may mitigate some of the historical inequities in the delivery of care. Future studies incorporating larger, more diverse populations, robust adjustment for clinical and social determinants of health, and qualitative assessments of barriers to treatment are needed to better understand and address the drivers of disparities in mTNBC outcomes.