Abstract
AIMS: Clinical guidelines for breast cancer management have evolved in the past decade. However, limited evidence exists regarding uptake of novel drug classes in management of hormone receptor-positive (HR+) metastatic breast cancer (MBC) in the USA and whether disparities exist by race and ethnicity. METHODS: Using SEER-Medicare databases, we identified 4404 women aged ≥66 years diagnosed with HR+ de novo MBC (dnMBC) between 2010 and 2019. Age-standardized rates for receipt of first-line treatment were calculated. Age-adjusted rate ratios (RRs) and 95% confidence intervals (CIs) were estimated using Poisson regression to compare rates among non-Hispanic Black (NHB) and Hispanic patients with non-Hispanic White (NHW) patients. RESULTS: Among patients with HR+/human epidermal growth factor receptor 2-negative (HER2-) dnMBC after 2015, 48.6% received first-line treatment with aromatase inhibitors (AIs) and 22.8% with AIs plus cyclin-dependent kinase (CDK) 4/6 inhibitors. Rates for AIs + CDK4/6 inhibitors increased (per 1000 person-years: 262.2 in 2015; 452.8 in 2019). Compared with NHW, NHB (RR [95% CI%]: 0.87 [0.63-1.21]) and Hispanic patients (RR [95% CI%]: 0.74 [0.51-1.08]) were less likely to receive AIs + CDK4/6 inhibitors. For HR+/HER2+ dnMBC, 29.7% of patients received pertuzumab, 23.1% with AIs and 10.8% with AIs + trastuzumab. Rates for pertuzumab increased, while rates for trastuzumab monotherapy declined. Compared with NHW, NHB and Hispanic women were less likely to receive anti-HER therapy (RR [95% CI]: 0.51 [0.35-0.73] and 0.58 [0.39-0.86]). CONCLUSION: There is a temporal increase in first-line treatment with AIs + CDK4/6 inhibitors and pertuzumab in dnMBC in the USA but with significant disparities by race and ethnicity.