Pragmatic predictors of response to abiraterone in metastatic castrate resistant-prostate cancer.

Abstract

286 Background: In patients with metastatic castrate resistant prostate cancer (mCRPC) there are several treatment options that have been shown to prolong survival. These treatments have not been directly compared in randomized clinical trials. In addition, the optimum sequencing of treatments for an individual patient has not yet been established. There is early evidence there are genetic predictors of response to enzalutamide and abiraterone, but these are likely to be some way off routine clinical application. There is a more urgent need for a practical method of identifying patients who are unlikely to respond to a particular treatment so that a more appropriate therapy can be used. Methods: A retrospective analysis of 47 consecutive patients with mCRPC treated in a single cancer centre was conducted. All patients were treated according to the following treatment sequence: (1) continuous LHRH analogues (LHRHa); (2) antiandrogen therapy and subsequent withdrawal; (3) docetaxel plus prednisolone; (4) abiraterone. Data were collected on patient and disease demographics, treatment received and response. Definitions of relapse and treatment response were as per the Cou-301 trial. Results: 47 patients were identified. Median age was 76 years (range 55-86). Only 1 patient had a Gleason score ≤ 6. Median duration of response to abiraterone in responders versus non-responders of each line of treatment was compared using the unpaired t-test. The results are displayed in Table. Conclusions: Time to progression on LHRHa, no response to bicalutamide and duration of biochemical response to docetaxel were strong predictors of a poor response to abiraterone. Further statistical analysis is planned, and these observations require prospective validation. [Table: see text]