Abstract
BACKGROUND: Improved clinical outcomes have been observed in patients with metastatic castration-sensitive prostate cancer (mCSPC) who experience deep prostate-specific antigen (PSA) responses after treatment with androgen receptor pathway inhibitors (ARPIs). OBJECTIVE: This retrospective longitudinal study aimed to compare real-world PSA90 response (≥90% reduction from pretreatment levels) in Black patients with mCSPC treated with apalutamide vs abiraterone acetate. METHODS: Electronic medical record (EMR) data from Precision Point Specialty Analytics were linked to claims data from the Komodo Research Database. Black adult patients with mCSPC who initiated apalutamide or abiraterone acetate on or after 9/17/2019 were included. Inverse probability of treatment weighting was used to balance patient characteristics between treatment cohorts. PSA90 was evaluated during the on-treatment period, defined as the time from index date to the earliest of treatment discontinuation, initiation of a new ARPI or radiopharmaceutical, or end of insurance claims activity or clinical activity. Weighted Kaplan-Meier curves and hazard ratios (HRs) were used to compare PSA90 responses between treatment cohorts. RESULTS: This study included 363 patients, of which 236 initiated apalutamide and 127 initiated abiraterone acetate. At 6 months following treatment initiation, a greater proportion of patients treated with apalutamide (65.4%) vs abiraterone acetate (49.0%) achieved a PSA90 response. Patients who initiated apalutamide vs abiraterone acetate were 66% more likely to achieve a PSA90 response within 6 months of treatment initiation (HR, 1.66; 95% confidence interval, 1.18-2.35; P = .004). The median time-to-PSA90 response was approximately 6 months earlier for patients treated with apalutamide (3.3 months) compared with abiraterone acetate (9.1 months). DISCUSSION: This study leveraged robust information from combined insurance claims and routinely collected EMR data to evaluate PSA90, a clinically relevant biomarker of treatment response, among Black patients with mCSPC. These results are among the first in this understudied patient population and suggest that a deeper and earlier PSA response achieved with apalutamide relative to abiraterone acetate can extend to Black patients in a real-world US clinical setting. CONCLUSION: Black patients treated with apalutamide experienced significantly higher PSA90 response rates than those treated with abiraterone acetate, suggesting possible clinical benefits from early treatment response in this population.