Prognostic Value of MammaPrint in Diverse Populations: Evaluating Racial Disparities in Breast Cancer Outcomes

MammaPrint (MP), a 70-gene expression profile assay, informs treatment decisions in early-stage breast cancer by classifying patients into high or low risk of recurrence categories. However, racial disparities in breast cancer outcomes necessitate an evaluation of MP's prognostic utility across diverse populations. This study explores differences in MP scores and associated outcomes among women of various racial backgrounds.

We retrospectively analyzed women with early-stage breast cancer who underwent MP testing (2013-2023) at University Hospitals Seidman Cancer Center. Patients were stratified by self-reported race and MP scores (high v low risk). Clinical outcomes, including recurrence-free survival (RFS) and overall survival (OS), were compared using Kaplan-Meier and Cox proportional hazards models.

Among 1,349 women, 15.7% were African American (AA), 83.4% White, 0.6% Asian, and 0.3% from other racial groups. Overall, 64.7% had low-risk and 35.3% had high-risk scores. AA women had a significantly higher proportion of high-risk MP scores compared with White women (49.1% v 32.7%). Although the 5-year RFS rates were comparable between AA and White women (76.5% v 77.2%), the 5-year OS rates were slightly lower for AA women compared with White women (77.8% v 78.2%). MP remained prognostic for RFS at 3, 5, and 10 years regardless of race. Multivariable analysis revealed no significant differences in OS (hazard ratio [HR], 0.94 [95% CI, 0.47 to 1.89]; P = .866) or RFS (HR, 0.83 [95% CI, 0.43 to 1.59]; P = .572) between AA and White women after adjusting for MP risk groups and other clinical factors. High-risk MP scores were associated with worse OS (HR, 3.06 [95% CI, 1.64 to 5.70]; P < .001) and RFS (HR, 2.68 [95% CI, 1.55 to 4.62]; P < .001) compared with low-risk scores. Other factors associated with worse RFS and OS were tumor size, nodal involvement, and age. Interaction models indicated no difference is OS or RFS in AA women and White women with either low-risk or high-risk MP, respectively.

Despite AA women exhibiting a higher proportion of high-risk MP scores, survival outcomes were comparable with those of White women. These findings underscore MP's consistent prognostic performance across racial groups but further highlight the need to address additional clinical and social determinants influencing breast cancer outcomes beyond genomic risk alone.