Adjuvant enzalutamide (Enza) for men with non-metastatic high-risk prostate cancer (HRPCa) after radical prostatectomy (RP).

Abstract

88 Background: Management of HRPCa is a clinical challenge. Novel AR inhibitors could potentially impact outcome in HRPCa men following RP. We conducted a phase II study evaluating the efficacy/safety of Enza in men with HRPCa following RP. Methods: HRPCa pts (≥pT3a, GS≥8, iPSA ≥20 ng/mL, +ve lymph nodes (LN), or ≥35% chance of biochemical recurrence (BCR) at 5 yrs based on MSKCC’s nomogram) with undetectable PSA within 3 months from RP were eligible. Enza 160mg PO daily was given in 28-day cycles until disease progression, intolerability, consent withdrawal, or study completion at 24 months. Accrual goal was N=40 to provide 80% power to detect a 75% decrease in the risk of BCR from historical 55% rate. BCR was defined as PSA ≥0.2ng/mL on 2 consecutive lab results or any PSA rise that resulted in subsequent therapy. Results: 42 men enrolled. Median age 59 (range 43-70), based on biopsy 45% were GS7; 36% GS8, 19% GS9. 76% men had cT1, 24% cT2, median iPSA was 8.2 (range 2-77). On prostatectomy pathology: 50% had pT3b; 52% +ve margins; 50% SVI; 24% had +LN. 37 (88%) pts completed 24 planned cycles. Of the 5 pts who did not complete all cycles, 3 withdrew consent for toxicity (2 had G3 fatigue, 1 had G3 fatigue and arthralgias/myalgias), 1 had rising PSA requiring subsequent therapy, and 1 had financial concerns. With median follow-up of 31 months (range 2.5-44.5), 37 (88%) pts remain free of BCR. Of the 5 pts who developed BCR, 4 completed all 24 months on therapy. Median time to BCR was 31 months (range 13-40). Most common adverse events (AE) are listed (Table). Conclusions: Adjuvant Enza in men with HRPCa following RP is safe and relatively well-tolerated. Long-term safety, efficacy, and genomic correlations (including tumor RNA expression) are ongoing. Clinical trial information: NCT01927627. [Table: see text] </jats:p