Looking to possible predictive factors of primary resistance to abiraterone acetate (AA) and enzalutamide (ENZ) in pretreated patients (pts) with castration-resistant prostate cancer (CRPC).

248 Background: Abiraterone acetate (AA) and enzalutamide (ENZ) are new generation hormonal agents (NHA) which demonstrated a survival gain in patients (pts) with castration-resistant prostate cancer (CRPC) pre-treated with docetaxel. Although all patients eventually became resistant to these NHAs, some of them show primary resistance, defined as an early progression within the first 3 months, which leads to an early treatment interruption. In the present analysis we have tried to identify which factor, if any, may predict primary resistance to AA and ENZ. Methods: We evaluated a consecutive series of 57 pts, treated in our hospital in two successive named patient programs conducted in our hospital to allow pre-treated CRPC patients to receive NHAs before their approval in Italy: 26 received AA (1,000 mg po + prednisone 10 mg po daily) and 31 ENZ (160 mg po daily). For each pt we have recorded the pre- and post-NHA clinical history, the treatment details and outcomes. We have also assessed the ability of ...