The following is a summary of ”Attainment of early, deep prostate-specific antigen response in metastatic castration-sensitive prostate cancer: A comparison of patients initiated on apalutamide or enzalutamide,” published in the May 2023 issue of the Urologic Oncology by Lowentritt et al.

Deep prostate-specific antigen (PSA) response, defined as a ≥90% decline in PSA (PSA90), is an essential early response indicator for radiographic progression-free and overall survival in patients with metastatic castration-sensitive prostate cancer (mCSPC) treated with a next-generation androgen signaling inhibitor (ASI) such as apalutamide or enzalutamide. This study compared deep PSA responses between newly initiated enzalutamide and enzalutamide patients with mCSPC. Clinical data from 69 community urology practices were evaluated in the United States.

Patients with metastatic castration-resistant prostate cancer were categorized into cohorts based on their first dispensation (index date) of enzalutamide or enzalutamide. They were followed until the earliest treatment discontinuation, a new next-generation androgen receptor signaling inhibitor was initiated, or the end of data availability (03/05/2021). Inverse probability of treatment weights (IPTW) was utilized to minimize baseline confounding ≥PSA90 was the earliest PSA decline of 90% compared to PSA at baseline. The proportion of patients achieving PSA90 and time to PSA90 were reported using weighted Kaplan-Meier analysis and weighted Cox proportional hazards models. The apalutamide and enzalutamide cohorts, respectively, included 186 and 165 patients. 

After IPTW, patient characteristics were frequently well-balanced. At 6 months, patients initiated on apalutamide were 56% more likely than those created on enzalutamide to achieve PSA90 (P = 0.014). This result was still statistically significant after the observation period. The median time to reach PSA90 with apalutamide was 3.1 months, while enzalutamide was 5.2 months. Initiation of apalutamide was associated with a significantly greater likelihood of attaining ≥90% PSA reduction compared to initiation of enzalutamide in this real-world study. In addition, this profound PSA response was observed to occur sooner with apalutamide than with enzalutamide.

Source: sciencedirect.com/science/article/pii/S1078143923000893