Intermittent vs continuous docetaxel therapy in patients with metastatic castration-resistant prostate cancer - a phase III study (PRINCE).

Objective: To investigate non-inferiority of intermittent docetaxel compared to continuous docetaxel in patients with metastatic castration-resistant prostate cancer (mCRPC).

Patient And Methods: The investigator initiated randomised phase III study included 187 chemotherapy-naïve patients with mCRPC who were allocated to two treatment arms: intermittent docetaxel and continuous docetaxel. Docetaxel was applied in both arms as weekly (35 mg/m ) or 3-weekly (75 mg/m ). The primary endpoint was 1-year survival, which was tested for non-inferiority (margin δ = 0.125). The secondary endpoints were: overall survival (OS), progression-free survival (PFS), median time to treatment failure (TTF), and toxicity.

Results: Of 156 eligible patients, 78 were allocated to each arm. The intermittent treatment met the non-inferiority criteria for 1-year survival (two-sided 95% confidence interval, -0.12, 18, P = 0.022), but not for OS, according to the result of a post hoc analysis. The differences between the study arms in PFS and TTF were not significant. The median (range) treatment holiday in the intermittent arm was 110 (13-486) days, or 38% of the overall treatment duration. Safety profiles of both study arms were comparable. The main limitation of this study was that the planned number of patients could not be recruited.

Conclusion: Intermittent docetaxel chemotherapy was non-inferior to continuous therapy for 1-year survival; non-inferiority in regard to OS was not reached.