Metastatic castration-resistant prostate cancer primarily affects elderly men. In this post hoc analysis we investigated the safety and efficacy of abiraterone acetate in elderly (≥75 years) and younger (<75 years) patient subgroups at the prespecified interim analysis (55% of total overall survival [OS] events) for the COU-AA-302 trial.

Patients were stratified and randomized 1:1 to abiraterone acetate 1,000 mg plus prednisone/prednisolone 5 mg bid (abiraterone-prednisone) vs placebo plus prednisone/prednisolone 5 mg bid (prednisone alone). Co-primary end points were radiographic progression-free survival (rPFS) and OS. Median time to event and hazard ratio (HR) were estimated using Kaplan-Meier method and Cox model, respectively.

Elderly patients (n=350) treated with abiraterone-prednisone had significant improvements in OS and rPFS vs prednisone alone (HR=0.71 [95% CI 0.53-0.96] and HR=0.63 [95% CI 0.48-0.83], respectively), similar to younger patients (n=738, HR=0.81 [95% CI 0.63-1.03] and HR=0.49 [95% CI 0.40-0.59], respectively). All secondary end points favored the abiraterone-prednisone arm for both age subgroups. Specific adverse events with abiraterone-prednisone were similar between age subgroups. Elderly patients in both treatment arms had higher rates of fluid retention and cardiac disorders than younger patients, although rates of dose reduction or treatment interruptions due to adverse events were low in both age subgroups.

Abiraterone acetate demonstrated clinical benefit and was well tolerated in both elderly and younger men with chemotherapy-naïve metastatic castration-resistant prostate cancer, thus supporting it as a treatment option for elderly patients who may not tolerate other therapies with greater toxicity. ClinicalTrials.gov: NCT00887198.