Exploring the Clinical Benefit of Docetaxel or Enzalutamide After Disease Progression During Abiraterone Acetate and Prednisone Treatment in Men With Metastatic Castration-Resistant Prostate Cancer

Abstract

BackgroundAbiraterone acetate (AA) has demonstrated improved outcomes in men with metastatic castration-resistant prostate cancer (mCRPC). However, data are lacking on the effect of AA on subsequent efficacy of enzalutamide or docetaxel. Patients and MethodsWe included men with mCRPC who received AA and subsequent enzalutamide or docetaxel by August 12, 2013. Patients were separated into 3 groups: group A, treated with AA then enzalutamide before chemotherapy; group B, treated with AA then docetaxel; and group C, treated with AA and enzalutamide after chemotherapy. The primary objective was to describe the response and overall survival with subsequent therapy. ResultsThere were 28 evaluable patients who received enzalutamide after AA (9 in group A and 19 in group C) and 13 patients who received docetaxel after AA (group B). Group A patients had more visceral disease and higher baseline prostate-specific antigen (PSA) levels, and group C men had a higher level of pain and multiple poor prognostic features. Median progression-free survival was 3.6, 5.1, and 2.8 months, respectively, and median overall survival was 8.5, not reached, and 9.6 months, respectively. A ≥ 50% PSA decline was achieved in 11%, 63%, and 5% of group A, B, and C patients, respectively. Radiographic or clinical progression as best response was noted in 55.5%, 30.8%, and 68.4% in each respective group. ConclusionIn this chart review of consecutive men with progressive mCRPC after AA, we found modest activity for enzalutamide and docetaxel, with clear cross-resistance for AA and enzalutamide. These data might inform the complex treatment decisions after AA treatment.