Initial Results From A Phase Ii Study Of Increased-Dose Abiraterone Acetate In Patients With Castration Resistant Prostate Cancer (Crpc).

188 Background: Resistance to abiraterone is hypothesized to result from increased systemic or tumor androgen production, mutations in the androgen receptor (AR) signaling pathway leading to ligand-independent, autonomous AR activity, and/or AR-independent pathways. This study investigated the clinical benefit of maximization of androgen suppression by increasing the abiraterone acetate dose at the time of initial resistance to standard-dose therapy. Methods: Eligible patients had progressive metastatic CRPC per consensus criteria. No prior abiraterone, enzalutamide, or chemotherapy was allowed. All patients started therapy with abiraterone acetate 1,000 mg daily and prednisone 5mg BID. Patients achieving any PSA decline after 3 cycles continued abiraterone until PSA or radiographic progression. At progression the abiraterone acetate dose was increased to 1,000 mg BID, prednisone was maintained at 5mg BID, and patients were monitored for response for a minimum of 12 weeks or until a second PSA or radiogra...