Introduction

Deep prostate-specific antigen (PSA) response is an important early response indicator for achieving 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

Aim

To compare deep PSA response among patients with mCSPC newly initiated on apalutamide or enzalutamide

Patient Profile

Adult patients (age ≥18 years) were required to have evidence of metastatic disease prior to or on the index date in the absence of castration resistance

Methods

• Retrospective study
• The analysis included 186 mCSPC patients initiating apalutamide and 165 mCSPC patients initiating enzalutamide
• For the primary analysis, the time to which patients first achieved ≥90% relative decline in PSA (i.e., PSA90) from the most recent baseline value observed within 13 weeks of the index date was assessed during the first 6 months of the

Study Outcomes

The proportion of patients achieving PSA90 and time to PSA90 were reported using weighted Kaplan-Meier analysis and weighted Cox proportional hazards models

Results

• By 6 months, patients initiated on apalutamide had a 56% greater likelihood of attaining PSA90 than those initiated on enzalutamide (P = 0.014).

• This result remained significant through the end of the observation period.

• The median time to achieving PSA90 was 3.1 months with apalutamide and 5.2 months with enzalutamide.

  Conclusion

• Apalutamide initiation is associated with a significantly higher likelihood of achieving ≥90% reduction in PSA as compared to initiation of enzalutamide.
• This deep PSA response was observed to occur earlier with apalutamide treatment than with enzalutamide.

Reference

Urol Oncol. 2023 May;41(5):253.e1-253.e9