• Johann S de Bono, Simon Chowdhury, Susan Feyerabend, Tony Elliott, Enrique Grande, Amal Melhem-Bertrandt, Benoit Baron, Mohammad Hirmand, Patrick Werbrouck, and Karim Fizazi.
• The Institute of Cancer Research, London, UK. Electronic address: johann.de-bono@icr.ac.uk.
• Eur. Urol. 2018 Jul 1; 74 (1): 37-45.

BackgroundEnzalutamide and abiraterone acetate plus prednisone, which target the androgen receptor axis, have expanded the treatment of advanced prostate cancer. Retrospective analyses suggest some cross-resistance between these two drugs when used sequentially, but robust, prospective studies have not yet been reported.ObjectiveTo fulfil a regulatory postregistration commitment by evaluating the efficacy and safety of enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC) who progressed following abiraterone acetate plus prednisone treatment.Design, Setting, And ParticipantsMulticentre, single-arm, open-label study, enrolled patients with progressing mCRPC after ≥24 wk of abiraterone acetate plus prednisone treatment. All patients maintained castration therapy during the trial. Prior chemotherapy was allowed but not required.InterventionPatients received enzalutamide 160mg/d orally.Outcome Measurements And Statistical AnalysisThe primary endpoint was radiographic progression-free survival. Secondary endpoints were overall survival, prostate-specific antigen (PSA) response, and time-to-PSA progression. Safety data were also assessed. Kaplan-Meier methods were used to descriptively analyse time-to-event endpoints.Results And LimitationsOverall, 214 patients received enzalutamide treatment, 145 of whom were chemotherapy-naïve. Median radiographic progression-free survival was 8.1 mo (95% confidence interval: 6.1-8.3); median overall survival had not been reached. Unconfirmed PSA response rate was 27% (48 of 181). Median time-to-PSA progression was 5.7 mo (95% confidence interval: 5.6-5.8). The most common treatment-emergent adverse events were fatigue (32%), decreased appetite (25%), asthenia (18%), back pain (17%), and arthralgia (16%). No seizures were reported.ConclusionsEnzalutamide showed antitumour activity in some patients with mCRPC who had previously progressed following ≥24 wk of abiraterone acetate plus prednisone treatment.Patient SummaryPatients with mCRPC who progressed on previous abiraterone acetate plus prednisone treatment, with or without prior chemotherapy, received enzalutamide. Although cross-resistance between the two agents was observed in a majority of patients, some still benefited from enzalutamide treatment.Copyright © 2017 European Association of Urology. Published by Elsevier B.V. All rights reserved.

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