Abstract PO4-10-04: Treatment differences by race and age in metastatic hormone receptor-positive/HER2-negative breast cancer

Abstract Introduction: Black and younger patients are more likely to have aggressive forms of breast cancer. Endocrine therapy (ET) plus a CDK4/6 inhibitor is the standard of care first-line therapy for patients with hormone receptor-positive, HER2-negative (HR+/HER2-) metastatic breast cancer (MBC). Recent data has shown better outcomes with this approach compared to chemotherapy, even for patients with aggressive disease. Our study looked at differences in first-line treatment among Black and younger women with HR+/HER2- MBC. Methods: Clinical characteristics, treatment, and outcomes of patients diagnosed with HR+/HER2- MBC between 2011-2022 were retrieved from the UNC Metastatic Breast Cancer Database. Log binomial regression modeling compared treatment choices by group, and Cox proportional hazards regression modeling evaluated progression-free survival (PFS) from the start of treatment. Results: 524 patients were included in this analysis. 30% were young patients (< 50 years of age), 20% were Black patients, 62% had only 1 site of metastasis and 51% had visceral involvement. When looking at first-line treatment for metastatic disease, 21% of overall patients had received chemotherapy. The likelihood of receiving chemotherapy was higher for younger verses (vs) older patients (29% vs 18%, RR=1.63, p=0.004), for Black vs White patients (31% vs 18%, RR=1.71, p=0.002), and for those with visceral vs non-visceral involvement (26% vs 16%, RR=1.67, p=0.004). A model including age, race, and visceral involvement showed similar findings. Among patients who received ET as the first line treatment for metastatic disease, the likelihood of receiving CDK 4/6 inhibitors in addition to ET was lower for young Black patients compared to young White patients (41% vs 74%, RR=0.55, p=0.02). However, among older patients >=50, no significant difference was seen by race (Blacks 60% vs Whites 56%, RR=1.1, p=0.61). Adjusting for visceral involvement showed similar findings. Patients who received ET (with or without CDK 4/6 inhibitors) had better PFS compared to patients receiving chemotherapy as first-line therapy (HR 0.65, 95% CI 0.49, 0.88, p=0.005), this held true after adjusting for age, race, treatment group and visceral involvement (HR 0.7, p=0.02). A stratified analysis showed similar findings within Black patients (HR 0.42, p=0.003), and young patients (HR 0.55, p=0.01). Conclusion: Overall, Black and younger patients were more likely to receive chemotherapy as the first-line treatment for metastatic disease. Among patients who received ET as the first-line treatment for MBC, young Black patients were less likely to receive CDK 4/6 inhibitors compared to young White patients. Further studies are needed to outline the multi-level factors contributing to the identified disparities in care among patients with HR+/HER2- MBC. Citation Format: Yara Abdou, Joannie Ivory, Allison Deal, Ally Wardell, Amy Wheless, Claire Dees, Lisa Carey. Treatment differences by race and age in metastatic hormone receptor-positive/HER2-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-10-04.