Real-World Early Prostate-Specific Antigen Response Comparison Among Patients with Metastatic Castration Sensitive Prostate Cancer Treated with Apalutamide or Abiraterone Acetate in the United States

Background Despite the availability of several androgen receptor pathway inhibitors for the treatment of patients with metastatic castration-sensitive prostate cancer (mCSPC), there has been a lack of head-to-head randomized clinical trials to evaluate their comparative efficacy in this population. Objective This real-world study provides a comprehensive and robust comparison of the decline in prostate-specific antigen ≥90% (PSA90) among patients with mCSPC who initiated apalutamide or abiraterone acetate in the United States. Methods Clinical data were collected from US community urology practices by Precision Point Specialty Analytics and linked with administrative claims from the Komodo Health Solutions Research Database. Patients with mCSPC were included in apalutamide or abiraterone acetate cohorts based on their first dispensation/paid claim on or after September 17, 2019 (index date), and followed to the earliest of treatment discontinuation or switch, end of insurance/clinical activity, or end of data availability (Dec. 31, 2023). Inverse probability of treatment weighting balanced potentially confounding patient characteristics. PSA90 response by 6 months post index was compared between the cohorts using weighted Kaplan-Meier analysis and time to PSA90 response was compared using a weighted Cox model with a time-varying treatment effect. Results The study included 1351 patients in the apalutamide cohort and 1003 patients in the abiraterone acetate cohort. By 6 months, 61.4% of the weighted apalutamide cohort and 45.9% of the weighted abiraterone acetate cohort achieved a PSA90 response. Compared with abiraterone acetate, patients treated with apalutamide were 73% more likely to achieve a PSA90 response at 6 months (weighted hazard ratio, 1.73; 95% confidence interval, 1.44-2.08; P < .001). The median time to PSA90 response was 3.8 and 8.7 months in the apalutamide and abiraterone acetate cohorts, respectively. Conclusions The results of this study confirm that patients with mCSPC treated with apalutamide have significantly higher rates of PSA90 response compared with abiraterone acetate after 6 months of treatment. Real-world evidence highlights apalutamide as an important treatment option to improve the prognosis of patients with mCSPC.