Do Racial and Income Disparities Exist in the Application of 21‐Gene Recurrence Score?

Background The 21‐gene recurrence score is a useful tool to predict the recurrence risk in patients with early hormone receptor positive (HR + ) and human epidermal receptor‐2 negative (HER2‐) breast cancer, which helps to determine those patients who may benefit from chemotherapy. Our goal was to assess whether there was a disparity in the use of the 21‐gene recurrence score, especially between races and income levels. Methods Using the SEER Medicare database, we analyzed breast cancer patients diagnosed from 2012 to 2017. Inclusion criteria were HR + /HER2‐ phenotype, clinical stages I and II in post‐menopausal women, and Stage 1 cancers in premenopausal women. Differences in the application of the 21‐gene recurrence score with regard to race and income level were studied using chi‐square analysis. Results Overall, 124 761 patients were included. Of these, 99.1% were females, and 32.9% had 21‐gene recurrence score testing. The median age was 70 years (range 27–100). Most patients had invasive ductal carcinoma (86.6%) followed by invasive lobular carcinoma (13.4%), of which 66.0% were stage I and 34.0% as stage II. When comparing subgroups based on testing, White race had a lower application rate (83.8% vs. 84.3%, p = 0.031), compared to African‐Americans (8.7% vs. 8.3%, p = 0.031). Similarly, patients with ≥ 10% poverty index showed a lower frequency of testing (46.0% vs. 47.3%, p < 0.001). However, clinically meaningful disparities by race or income were not observed. Underuse of 21‐gene recurrence score was more evident among older patients ( ≥ 65, 76.9% vs. 61%, p < 0.001), separated/divorced/widowed individuals (38.7% vs. 28.4%, p < 0.001), and those undergoing mastectomy (39% vs. 29.5%, p < 0.001) compared to breast‐conserving surgery. Conclusions No clinically significant disparities were observed in race or income level in the application of the 21‐gene recurrence score, which is reassuring, particularly as chemotherapy treatment regimens continue to trend appropriately trend toward de‐escalation. However, underuse was more evident among older patients, separated/divorced/widowed individuals, and those undergoing mastectomy, highlighting opportunities to improve equity and adherence to guideline‐based testing.