Abstract PD1-02: Racial and Socioeconomic Disparities in Patterns of Metastatic Disease Presentation and Treatment Among Patients With de novo Metastatic HR-Positive, HER2-Negative Breast Cancer

Abstract Background: Hormone receptor-positive (HR+) breast cancer is the most common form of metastatic breast cancer in the US, and first-line treatment with endocrine therapy (ET) plus a CDK4/6 inhibitor (CDK 4/6i) has substantially improved overall survival. Despite advances, Black and Hispanic patients (pts) continue to fare worse than other racial and ethnic groups. However, limited data exist on how patterns of metastatic presentation and timing of treatment initiation vary by race and socioeconomic status, specifically among pts with de novo metastatic HR+/HER2- breast cancer. Methods: Pts diagnosed with de novo metastatic HR+/HER2− breast cancer between 2010–2022 were identified using the National Cancer Database (NCDB). Sociodemographic and clinical characteristics were compared across racial/ethnic groups. Pattern of metastatic spread at diagnosis and time from diagnosis to initiation of ET, chemotherapy, and radiation therapy were assessed. Of note, CDK4/6i are not coded specifically in NCBD and are categorized as chemotherapy. Multivariable linear regression was used to examine differences in time (in days) to treatment by race/ethnicity, insurance status, area-level income and education, and facility type, adjusting for relevant clinical covariates. We calculated regression coefficients (β) and 95% CIs to determine differences in treatment timing. Results: A total of 72,874 pts were identified with de novo metastatic HR+/HER2− breast cancer. Mean age was 63.4 years (SD, 13.8); 74.2% were White, 15.1% Black, 6.2% Hispanic, and 3.5% Asian/Pacific Islander. At diagnosis, 5.7% presented with brain metastases, 44.2% with bone-only disease, and 36.9% with visceral disease. Of pts with bone only metastatic disease, a higher proportion were White (66.3%) compared to 60.8% Hispanic, 58.4% Asian/Pacific Islander, and 57.9% Black (p.001). A higher proportion of Black (43.4%) and Asian/Pacific Islanders (42.5%) had visceral metastases as compared to White pts (36.9%) (p.001). Brain metastases were less common overall, but Hispanic (7.5%) and Black (6.4%) pts had higher rates than White pts (5.7%) (p.001). ET was the first line of treatment in 78.8% of pts, with lower rates in Black (73.3%) and Hispanic (76.8%) pts compared to White pts (80.1%) (p.001). Chemotherapy was administered to 58.9% of pts, and radiation therapy to 32.5%, with significant variations by race/ethnicity. In adjusted models, Black (vs. White) race was associated with delayed initiation of ET (β = 6.6 days; 95% CI, 4.5–8.8), chemotherapy (β = 3.6; 95% CI, 1.4–5.8), and radiation (β = 11.3; 95% CI, 5.9–16.7). Compared with White pts, delays were also observed for Hispanic pts across all modalities: ET (β = 8.3; 95% CI, 5.2–11.5), chemotherapy (β = 12.3; 95% CI, 9.2–15.5), and radiation therapy (β = 18.6; 95% CI, 11.0–26.2). Community or integrated network facilities and those residing in lower income and education areas were associated with ET delays; Medicaid/Medicare insurance was associated with delays in chemotherapy initiation (β = 11.9; 95% CI, 5.0–18.7, β = 11.6; 95% CI, 3.7–19.6, respectively). Presence of brain metastases was associated with shorter time to initiation for all treatments. Conclusions: Among pts with de novo metastatic HR+/HER2− breast cancer, racial and socioeconomic disparities were observed in patterns of metastatic disease at presentation as well as time to treatment initiation. Black and Hispanic pts were more likely to present with visceral or brain metastases and experienced longer time to treatment initiation, independent of clinical and system-level factors. These findings highlight persistent inequities in access to timely cancer care in the metastatic setting in the US. Citation Format: S. Poland, J. Freeman, M. Hennessy, W. Guo, A. Ravichandran, R. Nanda. Racial and Socioeconomic Disparities in Patterns of Metastatic Disease Presentation and Treatment Among Patients With de novo Metastatic HR-Positive, HER2-Negative Breast Cancer abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PD1-02.