There are significant racial disparities in the delivery of HER2-targeted therapy for breast cancer, investigators have found.

A review of Medicare beneficiaries with incident stage I-III HER2-positive breast cancer showed that black women were 25% less likely than white women to receive adjuvant trastuzumab (Herceptin) within a year of diagnosis, reported Dr. Katherine Reeder-Hayes and her colleagues at the University of North Carolina at Chapel Hill.

In addition, the investigators found that about one-half of Medicare-insured patients with HER2-positive tumors did not receive HER2-targeted therapy, despite the well-known clinical benefits in this population.

“These findings have several troubling implications. First, although this study did not examine survival outcomes, the low overall rates of use among patients with stage II and III disease raise concerns for widespread underuse of trastuzumab in this age group. Second, the racial findings suggest that the presence of a clear biologic predictor of treatment benefit, in this case the HER2 marker, does not mitigate the overall pattern of treatment disparity observed among black women with breast cancer,” they wrote (J Clin Oncol. 2016 April 11. doi: 10.1200/JCO.2015.65.8716).

The authors reviewed Surveillance, Epidemiology and End Results (SEER) Medicare data on 1,362 women with incidence stages I-III HER2-positive breast cancers in 2010 and 2011, and used insurance claims data to identify the use of adjuvant trastuzumab and chemotherapy agents within 12 months of diagnosis. The sample included 1,162 white women, 104 black women, and 96 women described as “other.”

The investigators found that just half of all white women (50%) and 40% of black women received at least some trastuzumab therapy.

In logistic regression analysis controlling for tumor characteristics, socioeconomic factors, and comorbidities, they found that compared with white women, black women had a risk ratio for receiving trastuzumab of 0.745 (P = .0097).

The investigators noted that in addition to the racial disparities, older women and those with more comorbidities were also less likely to get trastuzumab.

“However, given the sizeable benefit of trastuzumab, the overall aggressive biology of this subtype, and extensive literature documenting undertreatment of even healthy older patients, the hypothesis that age is used inappropriately to withhold trastuzumab-based therapy deserves further exploration,” they wrote.

The investigators called for the development of system-level interventions that can objectively identify patients eligible for HER2-targeted therapy, and for ongoing efforts to eradicate racial disparities in care.

The study was supported by grants from the National Institutes of Health and the University (NC) Cancer Research Fund.