Real-world comparative effectiveness of apalutamide versus enzalutamide for prostate-specific antigen response in metastatic castration-sensitive prostate cancer.

BACKGROUND

Deep and rapid prostate-specific antigen (PSA) response is an important indicator to consider in treatment decision-making given its predictive value for long-term clinical outcomes in metastatic castration-sensitive prostate cancer (mCSPC).

OBJECTIVES

This study compared early PSA90 response (⩾90% reduction in PSA levels) in a large and recent cohort of patients with mCSPC initiating apalutamide or enzalutamide in the United States.

DESIGN

A retrospective longitudinal analysis was conducted.

METHODS

Patients with mCSPC were identified from linked claims and electronic medical record data from the United States and categorized into the apalutamide or enzalutamide cohorts based on the first claim/dispensation on or after December 16th, 2019. To adjust for differences observed in patient characteristics between the two cohorts, inverse probability of treatment weighting was used. Weighted Cox proportional hazards models were used to compare PSA90 response (PSA measurement ⩾90% lower than the most recent pretreatment PSA value) by 6 months post treatment initiation between the apalutamide and enzalutamide cohorts.

RESULTS

Among 1296 patients with mCSPC treated with apalutamide and 1111 treated with enzalutamide, pretreatment characteristics were balanced after weighting. PSA90 response by 6 months was achieved by 61.7% of patients in the apalutamide cohort and 55.2% of patients in the enzalutamide cohort (weighted hazard ratio: 1.20 [95% confidence interval: 1.07, 1.36]; p = 0.003). Patients in the apalutamide cohort achieved a PSA90 response earlier than those in the enzalutamide cohort (median time to PSA90 response: 3.7 vs 4.9 months, respectively).

CONCLUSION

In a large, real-world, retrospective analysis, patients with mCSPC treated with apalutamide were associated with a significantly higher rate of early PSA90 response compared to enzalutamide.