The impact of the introduction of generic aromatase inhibitors on adherence to hormonal therapy over the full course of 5-year treatment for breast cancer

Background High out-of-pocket costs (OOPCs) often are found to be inversely associated with adherence to medical treatment. The introduction of generic aromatase inhibitors (GAIs) significantly reduced the OOPCs of patients. The objective of the current study was to explore the impact of the introduction of GAIs on adjuvant hormone therapy (AHT) adherence over the full course of breast cancer treatment. Methods Women aged >= 65 years who were diagnosed with hormone receptor-positive breast cancer from 2007 through mid-2009 were identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare-linked database. Multivariate logistic regression was used to estimate the likelihood of AHT initiation and an interrupted time series model was used to predict the association between the introduction of GAIs and AHT adherence. The model was stratified further using Medicare low-income subsidy (LIS) status. Results A total of 10,905 women were included, approximately 62.8% of whom initiated AHT within the first year of their breast cancer diagnosis. Adjusted adherence among LIS beneficiaries was 11.4% higher than among non-LIS beneficiaries (P < .001). Non-LIS beneficiaries had an overall decreasing trend of adherence (-0.035; P < .001) prior to the introduction of GAIs. They experienced a 3.4% increase in the slope 6 months after the first GAI, anastrozole, entered the market, and an additional 0.8% increase in the slope 6 months after letrozole and exemestane were introduced (P < .001). Adherence change among LIS patients was small and statistically insignificant. Conclusions With the introduction of GAIs, the decrease trend of adherence to therapy atteunated over the course of treatment. Although the successful implementation of the Medicare LIS program minimized the OOPCs for financially vulnerable patients, policymakers should be cautious not to introduce disparities for those who may be of low income but ineligible for such a program.