A population-based study comparing outcomes for patients with metastatic castrate resistant prostate cancer treated by urologists or medical oncologists with first line abiraterone acetate or enzalutamide

Objectives — To compare toxicity and all-cause mortality for mCRPC patients receiving first line oral systemic therapy prescribed by medical oncologists and urologists.

Methods — Population-based retrospective cohort study of chemotherapy-naïve men aged ≥66 years treated for mCRPC with first-line abiraterone or enzalutamide based on administrative health data (Ontario, Canada, 2012-2017). Primary outcomes were hospitalizations/ER visits for any cause or treatment-related toxicity during first-line mCRPC treatment. Secondary outcome was all-cause mortality. We calculated hazard ratios (HRs) comparing outcomes for different medical specialties using multivariable Cox proportional hazards models.

Results — Among 3405 mCRPC patients, 2407 (70.7%) received abiraterone and 998 (29.3%) received enzalutamide. 1786 (52.5%) patients visited the ER or were hospitalized. Men treated by medical oncologists had an increased risk of hospitalization/ER visits (HR1.16, 95%CI 1.03-1.31; p=0.02), toxicity-related visits (HR1.34, 95%CI 1.08-1.69; p=0.01), and mortality (HR1.16, 95%CI 1.02-1.33; p=0.02) compared to urologists. Limited information was available, beyond PSA adjustment and prior treatment, on patient disease burden.

Conclusion — We observed fewer hospital visits overall and for treatment-related toxicity for mCRPC patients who were prescribed first line abiraterone or enzalutamide by urologists compared to medical oncologists. These differences may result from higher prostate cancer disease burden in patients managed by medical oncologists, and/or other unmeasured differences in patient management between specialties.