Background: The efficacy of docetaxel following exposure to androgen synthesis inhibitors such as KC or abiraterone acetate (AA) is unknown. Given the emerging use of pre-docetaxel AA and docetaxel’s inhibition of androgen signaling, we retrospectively evaluated the efficacy of every 3 week docetaxel with prednisone (DP) in mCRPC previously exposed to KC as compared to KC-naïve patients.
Methods: A randomized phase II trial of men with mCRPC treated with DP+AT-101 (bcl-2 inhibitor) vs. DP+placebo was analyzed (stratified for pain and performance status). Both arms were combined for analysis as no significant differences were seen. Overall survival [OS], progression-free survival [PFS], objective response [ORR], pain and PSA response rates were estimated with and without prior KC.
Results: Of 220 evaluable men, 40 (18.2%) received prior KC (median duration=2.0 months, maximum=31.1 months). These 40 men had less visceral disease (15% vs 28%), more prior radiotherapy (70% vs 51%), and increased prior radiological (38% vs 21%) or bone scan progression (55% vs 41%). Efficacy outcomes were not statistically different (table). After adjusting for baseline stratum and treatment group, prior KC did not appear to significantly change OS with DP-based therapy (HR 1.34, 95%CI: 0.86–2.09, p=0.20).
Conclusions: Similar outcomes were observed in mCRPC treated with DP-based therapy with or without prior KC. Given the marginally inferior survival with prior KC, evaluation of docetaxel outcomes following AA is of clinical importance, given its more potent CYP17 inhibition.
[Table: see text]