ESMO 2017: Outcomes of Prechemotherapy Abiraterone Acetate or Enzalutamide for mCRPC after ADT + Docetaxel or ADT alone for mHSPC

Madrid, Spain ( At this afternoon’s poster session at ESMO 2017, Dr. Francini and colleagues presented their results assessing the outcomes of prechemotherapy abiraterone or enzalutamide for metastatic castration-resistant prostate cancer (mCRPC) after patients were treated with ADT alone or ADT + docetaxel for metastatic hormone sensitivity prostate cancer (mHSPC). The CHAARTED trail [1] previously noted that the addition of docetaxel to ADT resulted in a hazard ratio of 0.56 (95%CI 0.44-0.70) for time to CRPC and resulted in prolongation of overall survival (OS) (HR 0.61, 95%CI 0.47-0.80). The hypothesis for the current study was that prechemotherapy abiraterone or enzalutamide would have greater activity after ADT + docetaxel compared to after ADT alone.

For this study, 102 men with mCRPC treated with prechemotherapy abiraterone or enzalutamide for mCRPC between 2014 and 2017 were included. Patients were grouped by use of docetaxel for mHSPC. This time frame was chosen considering that ADT + docetaxel became a valid therapeutic option for mHSPC in 2014 and thus time to prechemotherapy and follow-up were short. The endpoints included OS (time to death from all causes) from ADT start, time to abiraterone/enzalutamide start from ADT start, and OS from abiraterone/enzalutamide start. Survival outcomes were analyzed by Kaplan-Meier method. Among these patients, 50 (49%) had previously received ADT alone, while 52 (51%) had ADT + docetaxel. No statistically significant difference in OS from ADT start or from abiraterone/enzalutamide start was observed between the two cohorts. Notably, survival in both groups from ADT start was shorter than commonly reported. Yet, deaths in the ADT + docetaxel group were 12 (24.4%) vs. 21 (29.8%) in the ADT alone group, after a median follow-up of 24.4 and 29.8 months, respectively. This is important data, considering that few/any studies exist assessing outcomes of mCRPC therapeutic regimens after treatment of mHSPC with docetaxel.

The authors concluded that the efficacy of abiraterone/enzalutamide for mCRPC is similar regardless of previous docetaxel exposure in the mHSPC setting. It is possible that the patients selected for ADT + docetaxel had poorer prognostic factors and yet still did at least as well with abiraterone/enzalutamide and deaths were fewer. Larger sample sizes, longer follow-up, and better characterization of patient and tumor factors are needed to assess the efficacy of different sequences.

Speaker: Edoardo Francini, Dana-Farber Cancer Institute, Boston, United States of America

Co-Authors: S. Yip (Calgary, Canada) N. S. Ahmed (Calgary, Canada) H. Li (Calgary, Canada) L. Ardolino (Sydney, Australia) C. P. Evan (Boston, United States of America) M. Kaymakcalan (Boston, United States of America) G. K. Shaw (Boston, United States of America) P. Kantoff (New York, United States of America) M. Taplin (Boston, United States of America) N. Alimohamed (Calgary, Canada) A. M. Joshua (Sydney, Australia) D. Y. Heng (Calgary, Canada) C. J. Sweeney (Boston, United States of America)

Written By: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md at the European Society for Medical Oncology Annual Congress - September 8 - 12, 2017 - Madrid, Spain