310P - Identification of racial disparities across MammaPrint and BluePrint subtypes in HR+HER2- breast cancer

Background

Little is known about the underlying biology associated with worse outcomes in Black females with breast cancer (BC) compared to White females. Racial disparities in BC genomic subtypes have been observed with the MammaPrint (MP) risk of distant recurrence and BluePrint (BP) molecular subtyping signatures. To further understand these observations, we compared clinicopathologic features, MP/BP molecular subtype, and survival outcomes by race among females with hormone receptor-positive (HR+), HER2- early stage BC.

Methods

This study included 1,018 participants with HR+HER2- early BC: 509 Black females were matched by age and menopausal status to 509 White females. MP classified tumors as High-Risk or Low-Risk. BP together with MP further classified tumors as Luminal A-Type, Luminal B-Type, or Basal-Type. Recurrence-free survival (RFS) was compared between race and molecular subtype using Kaplan-Meier estimates and log-rank tests. A Cox proportional hazards model was used to analyze the association of MP, BP, race, and clinicopathologic features with survival.

Results

Black females compared to White females had an over-representation of HR+, Basal-Type tumors (11.0% vs 4.8% p<0.001) and worse 3-year RFS (90.1% vs 93.4%; p=0.0066). Basal-Type tumors had worse 3-year RFS (77.9%) compared to Luminal B-Type (91.2%) and Luminal A-Type (96.1%) tumors, independent of race. In a multivariate model controlling for confounders, High Risk Luminal B- and Basal-Type tumors had significantly worse 3-year outcomes compared to Luminal A-Type tumors, independent of race (Luminal B HR=2.87, [1.11-7.40], p=0.029; Basal HR=5.33, [1.56-18.15], p=0.007; Race HR=1.66, [0.87-3.14], p=0.122; LN+ HR=4.51, [2.43-8.37], p<0.001).

Conclusions

MammaPrint and BluePrint classification highlights racial disparities in the distribution of distinct High Risk molecular subtypes among HR+HER2- early BC. However, survival at 3 years was driven by molecular subtype, independent of race, after controlling for potential confounders. These data highlight the importance of tumor genomic testing to inform treatment decisions as we strive to reduce racial survival disparities among Black females with BC.

Clinical trial identification

FLEX Trial: NCT03053193 BEST Study: R01-CA204819.

Editorial acknowledgement

Legal entity responsible for the study

Agendia, Inc.

Funding

Agendia, Inc.

Disclosure

S. Reid: Non-Financial Interests, Personal, Speaker, Consultant, Advisor: Agendia. J. Wei; H. Ramaswamy; N. Stivers; A. Menicucci; W. Audeh: Financial Interests, Personal, Full or part-time Employment: Agendia. All other authors have declared no conflicts of interest.