Health-related quality of life effects of enzalutamide in patients with metastatic castration-resistant prostate cancer: an in-depth post hoc analysis of EQ-5D data from the PREVAIL trial

BACKGROUND: The effect of enzalutamide on health-related quality of life (HRQoL) in the PREVAIL trial in chemotherapy-naïve men with metastatic castration-resistant prostate cancer was analyzed using the generic EQ-5D instrument. METHODS: Patients received oral enzalutamide 160 mg/day (n = 872) or placebo (n = 845). EQ-5D index and EQ-5D visual analogue scale (EQ-5D VAS) scores were evaluated at baseline, week 13, and every 12 weeks until week 61 due to sample size reduction thereafter. Changes on individual dimensions were assessed, and Paretian Classification of Health Change (PCHC) and time-to-event analyses were conducted. RESULTS: With enzalutamide, EQ-5D index and EQ-5D VAS scores declined more slowly versus placebo and time to diverge from full health was prolonged. Average decline in EQ-5D index (−0.042 vs. –0.070; P < .0001) and EQ-5D VAS (−1.3 vs. –4.4; P < .0001) was significantly smaller with enzalutamide. There were significant (P < .05) between-group differences favoring enzalutamide in Pain/Discomfort to week 37, Anxiety/Depression at week 13, and Usual Activities at week 25, but no significant differences for Mobility and Self-care. The PCHC analysis showed more enzalutamide patients reporting improvement than placebo patients at weeks 13, 25, and 49 (all P < .05) and week 37 (P = .0512). Enzalutamide was superior (P ≤ .0003) to placebo for time to diverge from full health and time to first deterioration on Pain/Discomfort and Anxiety/Depression dimensions. CONCLUSIONS: This in-depth post hoc analysis showed that enzalutamide delayed HRQoL deterioration and had beneficial effects on several HRQoL domains, including Pain/Discomfort and the proportion of patients in full health, compared with placebo, and may help to support future analyses of this type. TRIAL REGISTRATION: NCT01212991