P2-07 APALUTAMIDE FOR HIGH-RISK LOCALIZED PROSTATE CANCER FOLLOWING RADICAL PROSTATECTOMY IN Apa-RP: A Multicenter, Open-Label, Single-Arm Phase 2 Study

Abstract

INTRODUCTION AND OBJECTIVES: Approximately 25% of patients (pts) with high-risk localized prostate cancer (HR LPC) experience disease recurrence within 2 years following radical prostatectomy (RP). The Apa-RP study (NCT04523207) investigated adjuvant treatment with apalutamide and androgen deprivation therapy (ADT) to determine if this combination improved the biochemical recurrence (BCR)-free rate in participants with HR LPC who had undergone RP, compared with historical data from pts with RP alone. METHOD(S): In this multicenter, open-label, single-arm, Phase 2 study conducted at 27 US community urologic practices, treatmentnaive pts with HR LPC who had undergone RP were treated with apalutamide (240 mg; once daily) and ADT for 12 cycles (1 cycle=28 days). The primary endpoint was confirmed BCR-free rate at 24 months, where BCR is defined as two sequential prostate-specific antigen (PSA) levels >0.2 ng/mL. Secondary endpoints included testosterone recovery rate and safety. Modified intention-to-treat analysis set is reported. RESULT(S): 108 pts were enrolled; the median age was 66.0 (range 46.0-77.0) years. The median pre-operative PSA and testosterone at baseline were 7.6 (range 2.2-62.7) ng/dL and 340.0 (range 43.0-939.0) ng/dL, respectively. Confirmed BCR-free rate was 100% at 24 months (90% confidence interval [CI] 93.0, 100.0) (Figure 1A); unconfirmed BCR-free rate at 24 months was 98.4% (90% CI 92.2, 99.7) (Figure 1B). The serum testosterone recovery (>=150 ng/dL) event rate was 76.4% (95% CI 65.0-84.5) at 12 months following treatment completion. Treatment-emergent adverse events (TEAEs) were reported by 99.1% (n=107) of pts during the study; 22.2% (n=24) were Grade 3 -4, and 14.8% (n=16) were serious AEs. 13.0% (n=14) and 10.2% (n=11) of pts required treatment dose reduction/interruption or discontinuation due to AEs, respectively. CONCLUSION(S): The Apa-RP study results suggest that treatment intensification with 12 months of apalutamide+ADT could become an option for patients with HR LPC undergoing RP, based on a 100% BCR-free survival. 76% of patients had testosterone recovery (>=150 ng/dL) 12 months after treatment completion. The safety profile of apalutamide + ADT was consistent with previous reports.