Does abiraterone withdrawal syndrome (AWS) exist also in metastatic castration-resistant prostate cancer (mCRPC) first-line setting?

344 Background: AWS is a recently phenomenon observed in mCRPC patients (pts) characterized by a PSA reduction with or without objective response after abiraterone acetate (AA) discontinuation. This syndrome has clinical features similar to antiandrogen withdrawal syndrome and was described in pts who treated with AA in the post-docetaxel setting. At the best of our knowledge, to date AWS was never described in chemo-naive mCRPC pts. Methods: We retrospectively reviewed clinical records of mCRPC pts treated with first-line AA at our Institution. All pts were treated with AA 1,000 mg + prednisone (PDN) 10 mg po daily; the treatment was continued until progression disease (PD) which required an imaging confirmation too. After PD, we also discontinued the PDN administration. For each pt we recorded pre and post-AA clinical history, treatment details and outcomes. AWS was defined by PSA reduction ≥ 25% compared to the AA-end values observed in the first month after AA stop. Results: From September 2014, eight...