Race/ethnicity and human epidermal growth hormone receptor 2–targeted therapy for breast cancer.

91 Background: Breast cancer is the most common cancer in the US. Up to 25% of breast cancers are classified as human epidermal growth factor receptor 2 (HER2)-positive and associated with an aggressive tumor burden. HER2-targeting monoclonal antibodies improves survival in patients with HER2-positive breast cancer. Prior work has demonstrated disparities in access to oncologic therapies among older women. Our study seeks to examine racial/ethnic disparities in receiving HER2-targeted therapies for patients with HER2-positive breast cancer and trends in use over time. Methods: In the Surveillance, Epidemiology and End Results (SEER) Medicare-linked database we identified women diagnosed with breast cancer from 2010 to 2019. We included those >66 years old who survived 12 months after diagnosis, were enrolled in Medicare Parts A/B for 12 months pre and post-diagnosis, and had local or regional stage HER2-positive cancer. Our primary outcome was receipt of HER2-targeted therapies in the 12 months after diagnosis. Our independent variable was race/ethnicity as measured by the validated Research Triangle Institute race/ethnicity codes in Medicare. Due to small sample sizes, we focus our analysis on White, Black, or Hispanic women. We used multivariable Modified Poisson regression to evaluate changes in the probability of HER2-targeted therapy receipt by race/ethnicity over time, adjusted for sociodemographics, cancer factors, and medical comorbidities. Results: Our cohort comprised 13,887 patients including 8.7% Black, 7.5% Hispanic, and 83.8% White (mean age 74.9). Overall, 7,351 (52.9%) received HER2-targeted therapies in the 12 months post-diagnosis, with use increasing over time in all racial/ethnic groups (Table). Compared with White patients, Black and Hispanic patients had a 19% (adjusted risk ratio [aRR] 0.81, 95% CI:0.69-0.96) and 27% (aRR 0.73, 95% CI 0.61-0.89) lower likelihood, respectively, of receiving HER2-targeted therapies from 2010-2011 (Table). By 2018-2019, no significant differences in receiving HER2-targeted therapies were observed across racial/ethnic groups. Conclusions: In a national cohort of Medicare enrollees with HER2-positive breast cancer, we observed significant racial/ethnic disparities which narrowed over time. Overall utilization rates were low. Future work is needed to understand how improved access to breast cancer treatments impact downstream outcomes. Use of human epidermal growth hormone receptor 2–targeted therapy from 2010-2011 and 2018-2019 by race/ethnicity. Race and Ethnicity Unadjusted Rates Adjusted Risk Ratios (95% CI)* 2010-2011 2018-2019 2010-2011 2018-2019 Black 36% 62% 0.81 (0.69-0.96) 0.97 (0.87-1.08) Hispanic 31% 68% 0.73 (0.61-0.89) 1.01 (0.92-1.12) White 42% 64% Reference Reference *Adjusted for age, marital status, region, breast cancer stage and year of diagnosis, and medical comorbidities.