EAU 2014 - Does Gleason score at initial diagnosis predict efficacy of abiraterone acetate (AA) therapy in patients with metastatic castration-resistant prostate cancer (mCRPC)? An analysis of AA phase 3 trials - Session Highlights

STOCKHOLM, SWEDEN (UroToday.com) - In this large multi-center study, authors retrospectively evaluated the efficacy outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate (AA) plus prednisone (P) vs P alone in pivotal studies COU-AA-301 (post-docetaxel) and COU-AA-302 (chemo-naïve), by Gleason score (≥ 8 or < 8), at initial diagnosis. In the entire cohort, 996 in COU-AA-302 and 1 088 patients in COU-AA-301 with mCRPC were treated with AA 1 g + P 5 mg po BID or placebo + P had GS data at diagnosis. Overall survival (OS), radiographic progression free survival (rPFS), and time to prostate-specific antigen progression (TTPP) were the efficacy end points evaluated in the study. Distributions and medians were estimated by the Kaplan-Meier method, and hazard ratio (HR) and 95% confidence interval were estimated by the Cox model.

eauThe proportion of patients with GS ≥ 8 and GS < 8 was similar across treatment groups and studies. Of patients with mRPC post-docetaxel, those who were treated with AA + P with GS ≥ 8 at initial diagnosis had significant improvement in OS, rPFS, and TTPP compared with those treated with prednisone alone. Moreover, of chemotherapy-naive patients with mRPC, those treated with AA + P with GS ≥ 8 or GS < 8 at initial diagnosis had significant improvement in rPFS and TTPP compared with those who were treated with prednisone alone.

Unlike in localized disease where Gleason score is strongly prognostic, in mCRPC it is not a strong prognosticator of survival. The impact of GS at initial diagnosis on response to AA therapy in patients with mCRPC is unclear. In this study, the benefit of AA + P vs P alone in post-docetaxel and chemo-naïve patients with mCRPC was shown, and it was independent of GS (≥ 8 or < 8) at the time of initial diagnosis. Perhaps from the presented results of this study, one can see that in the era of novel androgen signaling targeted agents, GS at initial diagnosis may not be a good predictor of efficacy with AA for patients with mCRPC.

Presented by M. Stöckle,1 T. Flaig,2 C.H. Ohlmann,3 H. I. Scher,4 J.S. De Bono,5 D. Rathkopf,4 C. J. Ryan,6 T. Kheoh,7 J Li,8 M. Todd,9 T.W. Griffin,10 A. Molina,11 and K. Fizazi12 at the 29th Annual European Association of Urology (EAU) Congress - April 11 - 15, 2014 - Stockholmsmässan - Stockholm, Sweden.

1Saarland University, Dept. of Urology and Children Urology, Homburg/Saar, Germany,2University of Colorado Cancer Center, University of Colorado School of Medicine, Dept. of Oncology, Aurora, United States of America, 3Saarland University, Dept. of Urology, Homburg/Saar, Germany, 4Memorial Sloan-Kettering Cancer Center and Weill Cornell Medical College, Dept. of Genitourinary Oncology Service, New York, United States of America, 5The Institute of Cancer Research and The Royal Marsden Hospital, Dept. of Drug Development, Sutton, United Kingdom, 6Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, Dept. of Medicine, San Francisco, United States of America, 7Janssen Research & Development, Dept. of Biostatistics & Programming, Los Angeles, United States of America, 8Janssen Research & Development, Dept. of Biostatistics Oncology, Raritan, United States of America, 9Janssen Global Services, Dept. of Oncology, Raritan, United States of America, 10Janssen Research & Development, Dept. Clinical Oncology, Los Angeles, United States of America, 11Janssen Research & Development, Dept. of Oncology Scientific Innovation, Menlo Park, United States of America, 12Institut Gustave Roussy, University of Paris Sud, Dept. of Uro-Genitologie, Villejuif, United States of America

Written by Reza Mehrazin, MD, medical writer for UroToday.com

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