Post Hoc Analysis of Rapid and Deep Prostate-specific Antigen Decline and Patient-reported Health-related Quality of Life in SPARTAN and TITAN Patients with Advanced Prostate Cancer

BACKGROUND: Adding apalutamide to androgen-deprivation therapy (ADT) resulted in a rapid (at 3- and 6-mo treatment) and deep prostate-specific antigen (PSA) decline (to ≤0.2 ng/ml or ≥90% from baseline), improved overall survival, reduced risk of disease progression, and prolonged health-related quality of life (HRQoL) in nonmetastatic castration-resistant prostate cancer (nmCRPC) in SPARTAN and metastatic castration-sensitive PC (mCSPC) in TITAN. OBJECTIVE: To evaluate the association of a rapid, deep PSA decline at 3 and 6 mo achieved with the addition of apalutamide to ADT with patient-reported outcomes (PROs) in SPARTAN and TITAN. DESIGN, SETTING, AND PARTICIPANTS: A post hoc analysis of SPARTAN and TITAN PRO data was performed. INTERVENTION: Apalutamide versus placebo plus concurrent ADT. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: PROs were assessed using Functional Assessment of Cancer Therapy-Prostate (FACT-P; SPARTAN and TITAN), Brief Pain Inventory-Short Form (BPI-SF; TITAN), and Brief Fatigue Inventory (BFI; TITAN) at baseline, prespecified cycles during treatment, and after progression for ≤1 yr. The association between a deep PSA decline at landmark 3 or 6 mo of apalutamide and the time to worsening of PROs was assessed using the Kaplan-Meier methodology and Cox proportional-hazard modeling. RESULTS AND LIMITATIONS: Among 806 SPARTAN and 525 TITAN apalutamide-treated patients, the median treatment duration was 32.9 and 39.3 mo, respectively. Patients achieving a deep PSA decline at 3 mo had longer time to worsening in FACT-P total, FACT-P physical well-being, BPI-SF worst pain intensity, or BFI worst fatigue intensity. The 6-mo PSA decline results were similar. Limitations of patient characteristics in clinical studies should be considered. CONCLUSIONS: Attaining a deep and rapid PSA decline at 3 mo with apalutamide plus ADT was associated with longer preservation of overall HRQoL and physical well-being in nmCRPC and mCSPC. PATIENT SUMMARY: Quality of life is maintained in individuals with advanced prostate cancer who achieve a deep prostate-specific antigen decline at 3 mo of apalutamide plus drugs that lower male sex hormones.