Socioeconomic and racial disparities in receipt of treatment among early-stage ER+/PR+ HER2- breast cancer: Insights from invasive breast cancer OncoDX recurrence score database.

520 Background: Oncotype DX Recurrence Score (RS) predicts recurrence risk and potential benefit from chemotherapy (CT) in early-stage ER+ and HER2- breast cancer (BC). However, real-world CT decision patterns remain poorly understood. This work evaluated how socioeconomic, racial and clinical factors influence CT decisions beyond RS-guided recommendations. Methods: We analyzed patients with early-stage ER+/PR+, HER2- BC in SEER OncoDX RS Database (2004-2019). Variables included age, rurality, poverty status, socioeconomic status (SES), RS, histology, tumor grade, nodal status, PR status, and CT receipt. Treatment disparities among patients with similar RS were evaluated using chi-square tests. Multivariable logistic regression model (MVA) identified independent predictors of CT utilization among patients with similar RS. Results: A total of 208,674 patients were included (median age 60). Median follow up was 4.9 years. Among postmenopausal (post-M, ≥50yrs) women with RS≥26 (CT indicated), lowest SES (60.6% vs 66.5% [highest], P