Abiraterone acetate plus prednisone versus prednisone alone in chemotherapy-naive men with metastatic castration-resistant prostate cancer: patient-reported outcome results of a randomised phase 3 trial.

Background: Abiraterone acetate plus prednisone significantly improves radiographic progression-free survival in asymptomatic or mildly symptomatic, chemotherapy-naive patients with metastatic castration-resistant prostate cancer compared with prednisone alone. We describe analyses of data for patient-reported pain and functional status in a preplanned interim analysis of a phase 3 trial.

Methods: Between April 28, 2009, and June 23, 2010, patients with progressive, metastatic castration-resistant prostate cancer were enrolled into a multinational, double-blind, placebo-controlled trial. Patients were eligible if they were asymptomatic (score of 0 or 1 on item three of the Brief Pain Inventory Short Form [BPI-SF] questionnaire) or mildly symptomatic (score of 2 or 3) and had not previously received chemotherapy. Patients were randomly assigned (1:1) to receive oral abiraterone (1 g daily) plus prednisone (5 mg twice daily) or placebo plus prednisone in continuous 4-week cycles. Pain was assessed with the BPI-SF questionnaire, and health-related quality of life (HRQoL) with the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire. We analysed data with prespecified criteria for clinically meaningful pain progression and deterioration in HRQoL. All patients who underwent randomisation were included in analyses.

Findings: 1088 patients underwent randomisation: 546 were assigned to abiraterone plus prednisone and 542 to placebo plus prednisone. At the time of the second prespecified interim analysis, median follow-up was 22·2 months (IQR 20·2-24·8). Median time to progression of mean pain intensity was longer in patients assigned to abiraterone plus prednisone (26·7 months [95% CI 19·3-not estimable]) than in those assigned to placebo plus prednisone (18·4 months [14·9-not estimable]; hazard ratio [HR] 0·82, 95% CI 0·67-1·00; p=0·0490), as was median time to progression of pain interference with daily activities (10·3 months [95% CI 9·3-13·0] vs 7·4 months [6·4-8·6]; HR 0·79, 95% CI 0·67-0·93; p=0·005). Median time to progression of worst pain was also longer with abiraterone plus prednisone (26·7 months [95% CI 19·4-not estimable]) than with placebo plus prednisone (19·4 months [16·6-not estimable]), but the difference was not significant (HR 0·85, 95% CI 0·69-1·04; p=0·109). Median time to HRQoL deterioration was longer in patients assigned to abiraterone plus prednisone than in those assigned to placebo plus prednisone as assessed by the FACT-P total score (12·7 months [95% CI 11·1-14·0] vs 8·3 months [7·4-10·6]; HR 0·78, 95% CI 0·66-0·92; p=0·003) and by the score on its prostate-cancer-specific subscale (11·1 months [8·6-13·8] vs 5·8 months [5·5-8·3]; HR 0·70, 95% CI 0·60-0·83; p<0·0001).

Interpretation: Abiraterone plus prednisone delays patient-reported pain progression and HRQoL deterioration in chemotherapy-naive patients with metastatic castration-resistant prostate cancer. These results provide further support for the efficacy of abiraterone in this population.