Abstract
This study examined biomarker alteration prevalence, treatment patterns, and clinical outcomes among patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer to investigate racial differences. Analysis of 2,384 patients from the Flatiron Health-Foundation Medicine clinico-genomic database (FH-FMI CGDB) (2017-2022) assessed PIK3CA, AKT1, PTEN, ESR1, and BRCA1/2 alterations via NGS testing. Treatment patterns and overall survival were evaluated. In the study population (13% Black, 87% White), Black patients had lower PIK3CA mutation rates (34% vs. 42%, p = 0.03). In first-line treatment, Black patients were less likely to receive CDK4/6 inhibitors (53% vs. 66%, p < 0.01) and more likely to receive chemotherapy (27% vs. 17%, p < 0.01). After adjustment, Black patients had 38% lower odds of receiving first-line CDK4/6 inhibitors and experienced significantly shorter median overall survival (34.1 vs. 42.1 months, p < 0.01). Significant differences exist in biomarker prevalence, treatment access, and survival outcomes in HR+/HER2- metastatic breast cancer by race, highlighting unmet medical needs.