Although biomarker testing for women with metastatic breast cancer has become more common in recent years, racial inequalities persist in terms of who gets access to these tests. 

Black, Latinx, and Asian patients with HR-positive, HER2-negative metastatic breast cancer were less likely to receive biomarker testing following their diagnosis than White patients, researchers reported at the 2025 ASCO Annual Meeting. 

The researchers used the company’s own de-identified, electronic-health record-derived database to gather information on 36,316 patients. All patients were adult women with metastatic HR-positive, HER2-negative breast cancer who were diagnosed between 2011 and 2024. The researchers tracked changes in testing rates for ESR1, PIK3CA, AKT1, PTEN, and germline BRCA alterations for these patients over time and used machine-learning to help extract data from the medical records. They calculated hazard ratios for access to biomarker testing, adjusting for co-variates such as age, disease stage, ECOG status, and year of diagnosis. 

Of the total population, 61.5% of patients were non-Latinx White, 9.7% were non-Latinx Black, 1.9% were non-Latinx Asian, and 6.1% were Latinx, whereas 20.8% of patients were of unknown race. 

Compared with White patients, Latinx patients had a hazard ratio (HR) of 0.88 for access to biomarker testing; Black patients had an HR of 0.87; and Asian patients also had an HR of 0.87. 

Part of these disparities were explained by social determinants of health, the researchers continued. The inequity between White and Latinx patients was reportedly mediated by residential segregation, lack of vehicle ownership, and limited proficiency in English. 

Black patients were less likely than White patients to undergo testing for ESR1 and PIK3CA alterations. Latinx patients were also less likely than White patients to receive PIK3CA testing, which the researchers wrote was mediated by limited English proficiency as well as residential segregation. 

“Asian, Black, and Latinx patients were generally less likely than their White counterparts to receive biomarker testing after a metastatic breast cancer diagnosis, especially for PIK3CA and ESR1. Social determinant of health factors explained some of these biomarker testing inequities. Equitable access to biomarker testing should be prioritized to ensure patients have access to the most effective therapies. Future research should examine whether racial/ethnic inequities in biomarker testing are associated with inequities in treatment and outcomes.” 

- Catherine Keane, RN, NP, senior clinical director at Flatiron Health, New York, and colleagues wrote. 

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Reference: https://meetings.asco.org/abstracts-presentations/248599 

Disclosures: Authors are employees of Flatiron Health and declared financial ties to Roche. See full abstract for details.  

Photo Credit: Getty Images 

By Andrew Polhamus