Hormone Therapy Adherence and Costs in Women With Breast Cancer

Objectives: To examine the association between adherence to hormone therapy and healthcare costs in Medicaid-enrolled women with breast cancer. Methods: This retrospective longitudinal study using South Carolina Medicaid claims data linked with the South Carolina Central Cancer Registry identified women who were diagnosed with non-metastatic breast cancer between 2000 and 2008 and received tamoxifen or aromatase inhibitors (AIs) only during the study period. All the patients were followed up for 1, 2, 3, or 4 years after initiation of hormone therapy. Adherence rate per year was measured as proportion of days covered (PDC) by tamoxifen or AIs. Yearly medical, pharmacy, and total healthcare costs per patient were measured across 4 years. Generalized linear regression with repeated measures was performed to examine the associations between medication adherence and healthcare costs. Results: The population consisted of 410 eligible women who filled at least 1 prescription for AIs (n = 224, 55%) or tamoxifen (n = 186, 45%) within 1 year after diagnosis of breast cancer. Mean PDCs (per year) ranged from 0.71 to 0.75 and more than 50% women were adherent to hormone therapy (PDC >= 0.8) each year during the 4-year period. After adjustment, adherence to hormone therapy was associated with 31% decrease in medical costs. However, total healthcare cost savings were not observed in women adherent to hormone therapy. Conclusions: Suboptimal adherence to hormone therapy was associated with higher medical costs across a 4-year period. Early adherence-enhancing interventions have the potential to improve health and economic outcomes in women with breast cancer.