Comparison of abiraterone acetate (Abi) versus ketoconazole (Keto) in chemotherapy-naive patients (CN-pts) with metastatic castration resistant prostate cancer (mCRPC).

260 Background: Abi is a standard treatment (tx) in CN-pts with mCRPC. It is a potent and selective CYP 17 inhibitor. However, in many countries where abi has not been approved yet, keto is used as an alternative CYP 17 inhibitor. Preclinical data suggests that keto is a less specific and potent inhibitor of CYP 17. Clinical data (Peer et al, Prostate 2014) suggests that in docetaxel (D) refractory mCRPC, the outcome of abi tx may be superior to keto. However, there are limited clinical data comparing both agents in CN-pts with mCRPC. We aimed to compare the clinical effectiveness of abi vs keto in CN-pts with mCRPC, who were treated after the year 2004 (approval of D for the tx of mCRPC). Methods: Records from 72 CN-pts with mCRPC treated with abi in 5 Israeli centers were reviewed retrospectively, and matched by pre-tx risk category (favorable, intermediate, poor; Keizman, Oncologist 2012) to pts treated with keto 200 - 400 mg 3x day (international database, n = 156, from 4 centers across the US and Isr...