Maintenance versus discontinuation of androgen deprivation therapy during continuous or intermittent docetaxel administration in castration-resistant prostate cancer patients: A multicentre, randomised Phase III study by the Piemonte Oncology Network

Abstract

Background: This study was designed to demonstrate the non-inferiority (NI) in overall survival (OS) of suspension of androgen deprivation therapy (ADT) versus maintenance and intermittent versus continuous docetaxel administration in metastatic castration-resistant prostate cancer (mCRPC) patients.

Patients and methods: mCRPC patients were randomised to first-line docetaxel with maintenance or suspension of ADT. Patients attaining a prostate-specific antigen (PSA) response after four chemotherapy cycles underwent second randomisation to receive continuous or intermittent docetaxel therapy. Six hundred patients were to be randomised to achieve 80% statistical power to demonstrate an NI hazard ratio (HR) of 1.25 of interruption versus maintenance of ADT.

Results: The trial was prematurely closed when 198 participants were randomised. OS was similar in patients who continued (N = 96) versus those who interrupted (n = 102) ADT during docetaxel therapy (HR 0.98, 95% confidence interval [CI] 0.72-1.33] and those on a continuous (N = 35) versus an intermittent (N = 42) docetaxel schedule (HR 0.86, 95% CI 0.55-1.43). No difference in radiological progression-free survival, PSA response, or toxicity was observed between the study arms. The actual NI hazard margins of OS in Arms A and B patients were 1.33 and 1.43, respectively.

Conclusions: This trial enrolled one-third of the planned patients; this main weakness dramatically limits the interpretation of the results. ADT discontinuation and switching to an intermittent schedule did not seem to affect docetaxel efficacy. The absence of testosterone recovery in the majority of patients could have been a contributory factor. In men with mCRPC, ADT discontinuation should only be done with regular biochemical and clinical monitoring, with the option of quickly restarting ADT at disease progression.

Keywords: Androgen deprivation therapy; Castration-resistant; Intermittent docetaxel; Prostate cancer.