Overall Survival with Apalutamide Versus Enzalutamide in Metastatic Castration-Sensitive Prostate Cancer.

introductionSurvival outcomes associated with different androgen receptor pathway inhibitors (ARPIs) prescribed for the treatment of metastatic castration (hormone)-sensitive prostate cancer (mCSPC) have not been directly compared. The objective of this study was to compare overall survival (OS) by 24 months among ARPI-naïve patients with mCSPC initiating apalutamide or enzalutamide.

methodsA retrospective, causal longitudinal inverse probability of treatment weighted analysis was conducted to compare OS between patients initiating apalutamide or enzalutamide between December 2019 and December 2023 using de-identified linked US clinical and insurance claims data. Patients were excluded if they had prior exposure to ARPIs, had evidence of castration resistance, had < 12 months of database activity prior to ARPI initiation, were diagnosed with other primary cancers, or were treated with other advanced prostate cancer (PC)-related treatment (except docetaxel). Using an intention-to-treat approach, weighted Cox proportional hazards models were used to compare OS by 24 months between patients treated with apalutamide or enzalutamide (primary analyses; exploratory analyses used all available follow-up).

resultsOverall, 1810 and 1909 ARPI-naïve patients who initiated apalutamide or enzalutamide, respectively, were included. Measured baseline characteristics between cohorts were well balanced after weighting (for both: mean age 73.0 years, ~ 60% white, ~ 23% black or African American, ~ 78% Medicare-insured, mean Quan-CCI 8.6, ~ 20% with visceral metastasis, 56.2% with de novo PC). At 24 months post index, there was a statistically significant 23% reduction in the risk of mortality among patients who initiated apalutamide compared with enzalutamide (hazard ratio [HR] 0.77; 95% confidence interval [CI] 0.62, 0.96; p = 0.019). Results remained consistent when using all available follow-up metrics (HR 0.77; 95% CI 0.64, 0.93; nominal p = 0.008).

conclusionIn this head-to-head causal analysis among ARPI-naïve patients with mCSPC, treatment with apalutamide resulted in better survival outcomes at 24 months compared with enzalutamide. Longer follow-up studies are required to fully determine the therapeutic comparator impact of these agents.