PROSPER: A Phase 3, Randomized, Double-blind, Placebo (PBO)-controlled Study of Enzalutamide (ENZA) in Men with Nonmetastatic Castration-Resistant Prostate Cancer (M0 CRPC)

BACKGROUND: Men with M0 CRPC and rapidly rising prostate-specific antigen (PSA) are at high risk of developing metastatic (M1) CRPC. ENZA improves overall survival (OS) and radiographic progression-free survival in men with M1 CRPC. We hypothesized that ENZA will improve metastasis-free survival (MFS) in men with M0 CRPC.

METHODS: Eligible men with M0 CRPC, PSA doubling time ≤ 10 mo and PSA ≥ 2 ng/mL at screening continued androgen deprivation therapy (ADT) and were randomized 2:1 to ENZA 160 mg or PBO.   The primary endpoint was MFS. Secondary endpoints included time to PSA progression, time to first use of new antineoplastic therapy, OS and safety.

RESULTS: In 1401 men, ENZA significantly prolonged median MFS (36.6 mo vs 14.7 mo [P < .0001]), time to first use of new antineoplastic therapy (39.6 mo vs 17.7 mo [P < .0001]) and time to PSA progression (37.2 mo vs 3.9 mo [P < .0001]) compared to PBO (Table). In the first interim analysis of OS there was a trend in favor of ENZA (hazard ratio [HR] = 0.80; P = .1519). Median duration of treatment was 18.4 mo vs 11.1 mo for ENZA vs PBO. Adverse events (AEs) were higher with ENZA vs PBO (any grade: 87% vs 77%; grade ≥ 3: 31% vs 23%; serious: 24% vs 18%); 10% with ENZA discontinued treatment due to AE vs 8% with PBO.

CONCLUSIONS: In men with M0 CRPC and rapidly rising PSA, ENZA treatment resulted in a clinically meaningful and statistically significant 71% reduction in the risk of developing M1 CRPC. AEs were consistent with the established safety profile of ENZA. Clinical trial information: NCT02003924.

references baseline characteristics ENZAADTPBO

Journal of Clinical Oncology 36, no. 6, 2018 Feb 28 [Epub]

Maha Hussain,1 Karim Fizazi,2 Fred Saad,3 Per Rathenborg,4 Neal D. Shore,5 Eren Demirhan,6 Katharina Modelska,7 De Phung,8 Andrew Krivoshik,9 Cora N. Sternberg10 

1. Northwestern University, Chicago, IL 
2. Institut Gustave Roussy, University of Paris Sud, Cancer Medicine, Villejuif, France 
3. Centre Hospitalier de l’Université de Montréal/CRCHUM, Montreal, QC, Canada 
4. Herlev Hospital, Herlev, Denmark 
5. Carolina Urologic Research Center, Myrtle Beach, SC 
6. Pfizer, Inc., San Francisco, CA
7. Pfizer, Inc., San Francisco, CA, US
8. Astellas Pharma Inc., Leiden, Netherlands
9. Astellas Pharma Inc., Northbrook, IL
10. San Camillo Forlanini Hospital, Rome, Italy

Journal of Clinical Oncology; DOI: 10.1200/JCO.2018.36.6_suppl.3
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