Abiraterone acetate, 1000 mg, once daily is approved for the treatment of metastatic castration-resistant prostate cancer (mCRPC) and high-risk metastatic castration-sensitive prostate cancer (mCSPC) in combination with prednisone, 5 mg, orally twice daily or once daily, respectively.1 However, the ideal dose of prednisone combined with abiraterone acetate is not known. In this issue of JAMA Oncology, Attard and colleagues2 report on the safety results of a phase 2 study of abiraterone acetate in combination with 4 different glucocorticoid regimens in the mCRPC setting.