Study Overview
Objective: To evaluate whether the addition of the potent androgen-receptor inhibitor (ARA) darolutamide to the standard doublet androgen-deprivation therapy (ADT) and docetaxel in metastatic, hormone-sensitive prostate cancer (mHSPC) would increase survival.
Design: A randomized, double-blind, placebo-controlled, multicenter, phase 3 study. The results reported in this publication are from the prespecified interim analysis.
Intervention: Patients with mHSPC were randomly assigned to receive either darolutamide 600 mg twice daily or placebo. All patients received standard ADT with 6 cycles of docetaxel 75 mg/m2 on day 1 every 21 days along with prednisone given within 6 weeks after randomization. Patients receiving luteinizing hormone–releasing hormone (LHRH) agonists as ADT were bridged with at least 4 weeks of first-generation antiandrogen therapy, which was discontinued before randomization. Treatments were continued until symptomatic disease progression, a change in neoplastic therapy, unacceptable toxicity, patient or physician decision, death, or nonadherence.
Setting and participants: Eligible patients included those newly diagnosed with mHSPC with metastases detected on contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI) and bone scan. Patients were excluded if they had regional lymph node–only involvement or if they had received more than 12 weeks of ADT before randomization. Between November 2016 and June 2018, 1306 patients (651 in the darolutamide group and 655 in the placebo group) were randomized in a 1:1 manner to receive darolutamide 600 mg twice daily or placebo in addition to ADT and docetaxel. Randomization was stratified based on the TNM staging system (M1a—nonregional lymph node–only metastasis, M1b—bone metastasis with or without lymph node, or M1c—bone metastases) as well as baseline alkaline phosphatase levels.
Main outcome measures: The primary end point for the study was overall survival. Other meaningful secondary end points included time to castration resistance, time to pain progression, time to first symptomatic skeletal event, symptomatic skeletal event-free survival, time to subsequent systemic antineoplastic therapy, time to worsening of disease-related physical symptoms, initiation of opioid therapy for ≥7 days, and safety.
Results: The baseline and demographic characteristics were well balanced between the 2 groups. Median age was 67 years. Nearly 80% of patients had bone metastasis, and approximately 17% had visceral metastasis. At the data cutoff date for the primary analysis, the median duration of therapy was 41 months for darolutamide compared with 16.7 months in the placebo group; 45.9% in the darolutamide group and 19.1% in the placebo group were receiving the allotted trial therapy at the time of the analysis. Six cycles of docetaxel were completed in approximately 85% of patients in both arms. Median overall survival follow-up was 43.7 months (darolutamide) and 42.4 months (placebo). A significant improvement in overall survival was observed in the darolutamide group. The risk of death was 32.5% lower in the darolutamide cohort than in the placebo cohort (hazard ratio [HR], 0.68; 95% CI, 0.57-0.80; P < .001). The overall survival at 4 years was 62.7% (95% CI, 58.7-66.7) in the darolutamide arm and 50.4% (95% CI, 46.3-54.6) in the placebo arm. The overall survival results remained favorable across most subgroups.
Darolutamide was associated with improvement in all key secondary endpoints. Time to castration-resistance was significantly longer in the darolutamide group (HR, 0.36; 95% CI, 0.30-0.42; P < .001). Time to pain progression was also significantly longer in the darolutamide group (HR, 0.79; 95% CI, 0.66-0.95; P = .01). Time to first symptomatic skeletal events (HR, 0.71; 95% CI, 0.54-0.94; P = .02) and time to initiation of subsequent systemic therapy (HR, 0.39; 95% CI, 0.33-0.46; P < .001) were also found to be longer in the darolutamide group.