Racial and Geographic Disparities in Endocrine Therapy Adherence Among Younger Breast Cancer Survivors

Objectives: African American (AA) women with breast cancer (BrCA) have higher mortality than any other race. Differential mortality has been attributed to nonadherence to endocrine therapy (ET). ET can lower the risk of dying by one third; yet 50% to 75% of all women are nonadherent to ET. Despite the wealth of research examining adherence to ET, understanding which groups of women at risk for poor adherence is not well established. The aim of this investigation was to describe ET adherence by race and geographic location among a cohort of younger BrCA survivors. Materials and Methods: Cancer registry records were linked to administrative data from Medicaid and a private insurance plan in South Carolina. Inclusion criteria included: European American (EA) or AA race, 3 years of continuous enrollment in the insurance plan after diagnosis, and BrCA diagnosis between 2002 and 2010. Adherence was measured by computing a medication possession ratio (MPR) based upon refill service dates and the number of pills dispensed. Adjusted least squared means were calculated by racial and geographic group using analysis of covariance methods. Results: The average MPR for EA women was significantly higher at 96% compared with 92% for AA women (P<0.01). After adjustment for years on hormone therapy, age, and number of pharmacies utilized, rural AA women had an average MPR of 90% compared with 95% for EA women (P<0.01). Conclusions: AA women residing in rural areas demonstrate significantly lower adherence compared with their EA counterparts. Interventions are needed to improve adherence that may ameliorate AA mortality disparities.