Will second-line nonsteroidal antiandrogen drugs (NSAA) after the failure of bicalutamide affect the therapeutic efficacy of the sequential abiraterone treatment?

Abstract

337 Background: Even in the era of novel targeted agents, second-line antiandrogens still have its effect on treating metastatic castration-resistant prostate cancer (mCRPC), especially for patients from undeveloped areas. Yet, it’s still uncertain if the prior use of second-line Non-steroidal antiandrogen Drugs (NSAA) would impact the efficacy of the sequential abiraterone (Abi) therapy. Methods: Eighty-seven patients from 2015 to 2017 were studied. All men were diagnosed with metastatic prostate cancer, and administrated with maximal androgen blockade (surgical or medical castration plus bicalutamide). After the median 32.0-Mo follow up, mCRPC was confirmed in the whole cohort. Abi was then administrated in these patients. Among them, 21 men previously received flutamide (FLU) as second-line NSAA hoping to postpone the initiation of the more expensive treatment. Therapeutic efficacy of Abi was analyzed and compared between those with and without prior second-line NSAA by Kaplan-Meier curves, Log-rank test and Cox regression models. Results: For patients with mCRPC, the prior exposure to FLU had no effect on the sequential treatment of Abi, in terms of either PSA progression-free survival (PSA-PFS, p = 0.967), radiographic progression-free survival (rPFS, P = 0.272), overall survival (OS, p = 0.606), or PSA response ( p = 0.370). However, when bringing ahead the observation point to the time of CRPC, those with second-line FLU showed better survival than those without, in either PSA-PFS (15.1 vs. 12.2-Mo, p = 0.120), rPFS (23.3 vs. 18.2-Mo, p = 0.029) or OS (not reach vs. 30.7-Mo, p = 0.306), though the difference of PSA-PFS and OS were not statistically significant. Conclusions: We firstly address the impact of the secondary NSAA on the efficacy of the sequential Abi treatment in mCRPC patients. Our study supported that, whether the patients received second-line NSAA prior to Abi should not be considered as an impact factor interfering physicians’ decision making of Abi treatment. Also, the switching treatment before Abi seemed to have a potential to extend the survival time of mCRPC patients by prolonging their PFS.