Elevated genomic risk and treatment gaps in Black patients with HR+ early breast cancer: A MammaPrint-based retrospective analysis.

Abstract

e12766 Background: Black women with hormone receptor-positive (HR+) early-stage breast cancer (EBC) have a 38% higher mortality rate than White women, even after adjustment for socioeconomic and access-related factors. Genomic differences may contribute. Some gene expression (GE) assays may underestimate risk in Black patients, while MammaPrint has shown greater sensitivity in identifying high-risk disease. Objective: To evaluate MammaPrint risk classification and treatment patterns in an exclusively Black cohort with HR+ EBC and compare results with historic White-majority populations such as the MINDACT trial. Methods: We performed a retrospective review of 116 self-identified Black/African American women aged ≥18 years with Stage I–III HR+ breast cancer who underwent MammaPrint testing between October 2024 and June 2025 at West Cancer Center and the University of Tennessee in Memphis. One Stage IV patient was grouped with Stage III. Tumor features, molecular subtype, and treatment data were collected. Statistical analyses included descriptive statistics and trend testing. This pilot cohort will expand to approximately 1,000 patients. Results: Of 116 patients, 64 (55.2%) were classified as High Risk and 52 (44.8%) as Low Risk; mean age was 62.5 years. A significant trend showed increasing High Risk classification by stage (50.6% Stage I, 66.7% Stage II, 88.3% Stage III/IV; P trend = 0.02). MammaPrint risk strongly correlated with molecular subtype (p < 0.001), with most Low Risk tumors being Luminal A and most High Risk tumors Luminal B. Despite over half the cohort being High Risk, only 42.2% received neoadjuvant and 18.8% adjuvant chemotherapy, raising concerns for potential undertreatment. In contrast, the MINDACT trial reported a High Risk rate of 35.8% in a largely White population. Conclusions: MammaPrint identified a substantially higher genomic risk burden in this exclusively Black cohort compared with historic White-majority populations. Although High Risk tumors were predominantly Luminal B, chemotherapy use remained low, highlighting gaps in the application of genomic risk stratification and the need for more equitable precision oncology.