Radium-223 plus Enzalutamide versus Enzalutamide in Metastatic Castration-Refractory Prostate Cancer: Final Safety and Efficacy Results.

Long-term safety of radium-223 with enzalutamide was confirmed in this clinical trial. PSA-PFS2 was prolonged with the combination compared with enzalutamide alone.

Previously, we showed the combination of radium-223 and enzalutamide to be safe and associated with improved efficacy based on a concomitant decline in serum bone metabolism markers compared with enzalutamide alone in a phase II trial of men with metastatic castration resistant prostate cancer (mCRPC) [1].

Secondary endpoints were not included in our initial report, and we include them herein, after a median follow-up of 22 months. These objectives included long term safety, PSA progression-free survival (PFS), and radiographic progression-free survival ; PSA-PFS2 (time from start of protocol therapy to PSA progression on subsequent therapy); time to next subsequent therapy (TTNT); and overall survival (OS). Survival analysis and log-rank tests were performed using the R statistical package v.4.0.2 (https://www.r-project.org). Statistical significance was defined as p < .05.

Of 47 patients (median age, 68 years), 35 received the combination and 12 enzalutamide alone. After a median follow-up of 22 months, final safety results did not show any increase in fractures or other adverse events in the combination arm. PSA-PFS2 was significantly improved, and other efficacy parameters were numerically improved in the combination over the enzalutamide arm.

The combination of enzalutamide and radium-223 was found to be safe and associated with promising efficacy in men with mCRPC. These hypothesis-generating results portend well for the ongoing phase III PEACE-3 trial in this setting.

The oncologist. 2021 Aug 22 [Epub ahead of print]

Benjamin L Maughan, Adam Kessel, Taylor Ryan McFarland, Nicolas Sayegh, Roberto Nussenzveig, Andrew W Hahn, John M Hoffman, Kathyrn Morton, Deepika Sirohi, Manish Kohli, Umang Swami, Kenneth Boucher, Benjamin Haaland, Neeraj Agarwal

Genitourinary Oncology, Huntsman Cancer Institute, Salt Lake City, Utah, USA., The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Center for Quantitative Cancer Imaging, Huntsman Cancer Institute, Salt Lake City, Utah, USA., Department of Radiology and Imaging Sciences, Huntsman Cancer Institute, Salt Lake City, Utah, USA., ARUP Laboratories, University of Utah, Salt Lake City, Utah, USA.

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