Real-World Overall Survival With Abiraterone Acetate and Enzalutamide in Patients With Chemotherapy-Naïve Metastatic Castration-Resistant Prostate Cancer From the Flatiron Electronic Health Records Database.

BACKGROUND

Patients with chemotherapy- and androgen receptor pathway inhibitor (ARPI)-naïve metastatic castration-resistant prostate cancer (mCRPC) have generally shown worse overall survival (OS) with abiraterone versus enzalutamide in claims database studies. Given limitations of claims data, analysis using detailed electronic health records (EHRs) is needed to confirm this finding.

METHODS

This EHR-based analysis (2014-2023) of the Flatiron Health database included patients with chemotherapy- and ARPI-naïve mCRPC who initiated first-line ARPI (abiraterone or enzalutamide). OS, treatment duration, and time to subsequent therapy were assessed. A subgroup analysis evaluated patients who received first-line ARPI only with no subsequent treatments. Kaplan-Meier method and Cox proportional hazards models evaluated time-to-event outcomes. Stabilized inverse probability treatment weighting (sIPTW) adjusted for baseline differences.

RESULTS

Among 2731 patients, 1316 received first-line abiraterone and 1415 enzalutamide (median follow-up: 21.8 and 23.2 months, respectively). sIPTW-adjusted median OS (24.6 vs. 25.8 months; hazard ratio [HR] 1.13; 95% confidence interval [CI], 1.03-1.23), treatment duration (7.9 vs. 9.5 months; HR 1.21; 95% CI, 1.11-1.31), and time to subsequent therapy (14.7 vs. 17.9 months; HR 1.20; 95% CI, 1.08-1.32) were shorter with abiraterone versus enzalutamide. Among the 40% with no subsequent treatment (n = 1102), sIPTW-adjusted median OS (14.0 vs. 17.7 months; HR 1.32; 95% CI, 1.14-1.53), and treatment duration (7.5 vs. 10.6 months; HR 1.30; 95% CI, 1.12-1.50) were also shorter with abiraterone versus enzalutamide.

CONCLUSIONS

Using more detailed data abstraction, these results confirm prior claims-based analyses showing that despite early use of subsequent therapy, first-line abiraterone is associated with shorter OS versus enzalutamide in ARPI- and chemotherapy-naïve mCRPC.

TRIAL REGISTRATION: Clinical Trial ID: NCT05968599.