The following is a summary of ”Comparison of prostate-specific antigen response in patients with metastatic castration-sensitive prostate cancer initiated on apalutamide or abiraterone acetate: A retrospective cohort study,” published in the May 2023 issue of the Urologic Oncology by Benjamin et al.
Deep prostate-specific antigen (PSA) response (≥90% reduction in PSA [PSA90]) is a significant early response indicator of radiographic progression-free survival and overall survival in patients with castration-sensitive metastatic castration-sensitive prostate cancer (mCSPC). This study compared PSA90 responses at six months between patients with mCSPC receiving apalutamide or abiraterone acetate, both inhibiting androgen receptor signaling. Clinical data from 77 community urology practices were analyzed in the United States. The first filled prescription (index date) for apalutamide or abiraterone acetate on or after September 17, 2019 (approval date of apalutamide for mCSPC) was used to classify patients with mCSPC into treatment cohorts.
Patients were observed from the index date until index treatment discontinuation, treatment switch, end of clinical activity, or end of data availability (September 17 2021). Inverse probability of treatment weighting (IPTW) was used to ensure baseline characteristics were distributed similarly across cohorts. PSA90 was the earliest achievement of ≥90% PSA reduction relative to baseline (most recent value within 13 weeks before index). Time to PSA90 was compared between cohorts using weighted Kaplan–Meier and Cox proportional hazards models.
The study criteria were met by 364 patients treated with apalutamide and 147 with abiraterone acetate. After IPTW, patient characteristics were well-balanced. Patients initiated on apalutamide were 53% more likely to attain PSA90 6 months post-index than those started on abiraterone acetate (P = 0.016). About 9 and 12 months post-index produced comparable outcomes (P≤ 0.019). The median latency to PSA90 for the apalutamide cohort was 3.5 months, while it was not reached for the abiraterone acetate cohort. Significantly more patients attained PSA90 with apalutamide than with abiraterone acetate in patients with mCSPC, and this response was achieved earlier with apalutamide.
Source: sciencedirect.com/science/article/pii/S1078143923000972