Background
Given the poor prognosis of patients with metastatic castration-resistant prostate cancer (mCRPC), interventions aimed at increasing adherence to oral treatments have the potential to improve patient outcomes. This study evaluates the impact of a patient stewardship assistance pilot program (stewardship program) on the adherence and persistence to oral treatments among patients with mCRPC at VA medical centers (VAMCs).
Methods
A non-randomized controlled study design and data from the VA Corporate Data Warehouse were used. The study included patients treated with an oral mCRPC therapy (i.e., abiraterone acetate or enzalutamide) between 08/2018 and 12/2019. Patients participating in the stewardship program formed the intervention arm and patients not participating the controls. Control patients were selected and matched 1:3 based on age, race and index year. The index date was the date of initiation of abiraterone acetate or enzalutamide. Outcomes included persistence (no gap >60 days of supply) and adherence (proportion of days covered [PDC] ≥80%) to oral mCRPC treatment post-index. Persistence and adherence were compared between the two arms using a Cox proportional hazard model and logistic regression model, respectively, adjusted for baseline characteristics.
Results
The study included 108 intervention patients (mean age: 74.6, 19.4% Black or African American, 44.4% from South, mean Quan-CCI: 6.7) and 324 control patients (mean age: 74.6, 19.4% Black or African American, 31.5% from South, mean Quan-CCI: 6.2). There was no statistically significant difference in persistence between the intervention and control arms (hazard ratio [95% confidence interval]: 0.84 [0.66-1.10], p-value: 0.211), with respective median times to discontinuation of 18 and 19 months. Over the first 12 months post-index, the proportion of adherent patients was not significantly different between the intervention arm and the control arm (50.6% vs. 50.9%; odds ratio [95% confidence interval]: 1.05 [0.80-1.38], p-value: 0.729).
Conclusions
In this racially diverse study of patients treated at VAMCs, high levels of persistence and adherence to oral mCRPC therapy were observed. The absence of any significant difference in adherence and persistence from the study intervention suggests that a stewardship assistance program aimed at improving adherence and persistence of patients with mCRPC may not be required at VAMCs.