Adherence to and persistence with adjuvant hormone therapy, healthcare utilization, and healthcare costs among older women with breast cancer: A population-based longitudinal cohort study.

Introduction: To assess associations between adherence to and persistence with adjuvant hormone therapy, healthcare utilization, and healthcare costs among older women with breast cancer.

Materials And Methods: This study was a population-based longitudinal cohort study using the Surveillance, Epidemiology, and End Results (SEER) registry linked with Medicare claims. This study included older women diagnosed with stage I-III hormone receptor-positive breast cancer from 2009 through 2017. Participants were considered adherent with a proportion of days covered (PDC) of 0.80 or more and persistent if they had no hormone therapy discontinuation, i.e., a break of at least 180 continuous days. Length of persistence was calculated as time from therapy initiation to discontinuation. All participants were followed for up to five years after hormone therapy initiation. Generalized linear mixed models with repeated measures or hurdle generalized linear mixed models in the event of excess zeroes were used to assess associations between adherence to and persistence with annual healthcare utilization and costs.

Results: This study included 25,796 women. Being adherent was associated with lower annual healthcare utilization, i.e., hospitalizations, hospital days, emergency room visits, and hospital outpatient visits. Persistence was associated with fewer annual hospitalizations, hospital days, emergency room visits, and hospital outpatient visits. Adherent participants had lower annual inpatient costs, outpatient costs, medical costs, and total healthcare costs despite higher prescription drug costs. Both being persistent and longer persistence were associated with lower inpatient costs, outpatient costs, medical costs, and total healthcare costs despite higher prescription drug costs.

Discussion: This study underscores the economic benefits associated with adherence to and persistence with adjuvant hormone therapy based on comprehensive measures for healthcare utilization and costs. To our best knowledge, this was the first study that reported total healthcare cost savings associated with adherence to and persistence with adjuvant hormone therapy.