Prognostic and Predictive Insights From Genomic Assays for Breast Cancer in Diverse Populations

Despite recent declines in breast cancer mortality rates, substantial disparities persist among race and ethnicity groups. Genomic assays are crucial for understanding the biological characteristics of tumors, providing valuable insights into prognosis and treatment response. Their integration into personalized clinical decision-making has notably enhanced outcomes, making these assays particularly valuable for underrepresented populations, which often face disproportionately poorer prognoses. Expanding research to evaluate the performance and predictive value of these assays across diverse groups is essential to ensure equitable benefits for all patients. This review evaluated the distribution of risk estimates from multigene assays, primarily focusing on 21-, 70-, and 50-gene signature assays, their predictive capabilities and impact on breast cancer recurrence and survival outcomes across race and ethnicity groups. Findings indicate that racial and ethnic disparities in breast cancer outcomes were influenced by a complex interplay of biological, social, and systemic factors. Black women were more likely to have aggressive tumor phenotypes, such as luminal B and basal-like subtypes, which contributed to poorer outcomes. These disparities persist even after adjusting for genomic assay results and molecular subtypes, suggesting that genomic factors alone cannot fully explain differences in clinical outcomes. Although subgroup analyses from 2 randomized clinical trials showed no apparent differences in the 21-gene signature's predictive value across racial groups, further research is needed to ensure that genomic assays are equitably calibrated for diverse populations. This review supports genomic assays as valuable tools for informing prognosis and treatment decisions in breast cancer; however, they do not fully capture factors associated with racial and ethnic disparities in outcomes. A comprehensive approach that integrates genomic data with a deeper understanding of social determinants and systemic inequities is essential to ensure all patients benefit equitably from advancements in personalized medicine.