Biochemical and objective response to abiraterone acetate withdrawal: incidence and clinical relevance of a new scenario for castration-resistant prostate cancer.

OBJECTIVE To describe the incidence and clinical relevance of biochemical and objective responses to abiraterone acetate (AA) withdrawal (AAWD) in patients with castration-resistant prostate cancer (CRPC). MATERIALS AND METHODS Twenty-six patients with progressive CRPC treated with first-line docetaxel-based chemotherapy were administered with AA at the standard dose of 1000 mg/day in combination with prednisone until progression. The patients were regularly followed up during treatment and after AAWD. RESULTS Nineteen of the 26 patients discontinued AA because of progression. Three of the patients undergoing AAWD experienced a biochemical response, which was accompanied by a metabolic and radiological response as revealed by choline positron emission tomography in 2 cases. CONCLUSION Regardless of the underlying molecular bases, AAWD response does not occur rarely. It is sometimes long-lasting and accompanied by a metabolic and radiographic improvement. AAWD response should be taken into account when further therapeutic strategies are planned in patients with CRPC with progressive disease during abiraterone therapy.