Treatment sequencing of abiraterone and enzalutamide in patients with mCRPC.

233Background: Abiraterone (Abi) and Enzalutamide (Enza) are among the treatment modalities available for treating metastatic castrate-resistant prostate cancer (mCRPC). This study aimed to analyze the efficacy of Abi and Enza as direct sequential treatments for patients with mCRPC. Methods: A single institution retrospective review was performed on 66 patients, in which 52 (79%) of the patients received Enza following Abi. The primary outcome measure was PSA response (50% PSA decline). Patients treated with taxanes between Abi and Enza were excluded from these analyses. Results: In patients treated first with Abi and second with Enza (n = 52), 35/52 (67%) responded initially to Abi. Following PSA progression or lack of initial response, all 52 patients were then treated with Enza, and 15/52 (29%) responded. Of the 17 patients that did not initially respond to Abi, 9 (53%) patients had a PSA response to Enza, in which 5/9 had a PSA decline ≥ 50%. 14 patients had a PSA decline ≥ 50% on initial Abi only (no...