Identification of racial disparities across MammaPrint and BluePrint subtypes in HR + HER2- breast cancer

We compared clinicopathologic features, MammaPrint and BluePrint molecular subtype, and outcomes by race among females with hormone receptor-positive (HR+), HER2- early-stage breast cancer (EBC). Of 1018 participants with HR+ HER2- EBC enrolled from two registries (BEST and FLEX), 509 White females were propensity score matched 1:1 to 509 Black females based on age and/or menopausal status. MammaPrint classified tumors as High-Risk or Low-Risk; and together with BluePrint, classified tumors as Luminal A-Type, Luminal B-Type, or Basal-Type. Recurrence-free survival (RFS) was analyzed by race and molecular subtype. Cox proportional hazards models assessed association of clinicopathologic features with outcomes. Basal-Type tumors were more prevalent among Black vs White participants (11.0% vs 4.8%, p < 0.001). Independent of race, participants with Basal-Type tumors had lower 3-year RFS (83.7%) compared to Luminal B-Type (93.7%) and Luminal A-Type (96.5%, p < 0.0001). Multivariate analysis revealed that participants with High-Risk, Luminal B- and Basal-Type tumors had significantly worse 3-year outcomes compared to Low-Risk Luminal A-Type, after controlling for race and potential confounders. Genomic classification identified higher proportions of High-Risk HR+ HER2- EBC among Black participants. Molecular subtype was independently prognostic of 3-year survival, supporting the prognostic and potentially predictive importance of genomic testing to reduce racial survival disparities among Black females with EBC.