GUIDE: a randomised non-comparative phase II trial of biomarker-driven intermittent docetaxel versus standard-of-care docetaxel in metastatic castration-resistant prostate cancer (clinical trial protocol).

To determine the efficacy and safety of intermittent docetaxel chemotherapy guided by circulating methylated glutathione S-transferase Pi-1 (mGSTP1) in men with metastatic castration-resistant prostate cancer (CRPC).

GUIDE (NCT04918810) is a randomised, two-arm, non-comparative phase-2 trial recruiting 120 patients at six Australian centres. Patients with Prostate Cancer Working Group-3 defined metastatic CRPC who are commencing docetaxel 75 mg/m2 q3w will be pre-screened for detectable mGSTP1 at baseline ± following two cycles of treatment. Those with detectable plasma mGSTP1 at baseline that becomes undetectable after two cycles of chemotherapy will be eligible for GUIDE. Prior to Cycle 4 of docetaxel, these patients are randomised 2:1 to one of two treatment arms: Arm A (cease docetaxel and reinstitute if mGSTP1 becomes detectable) or Arm B (continue docetaxel 75 mg/m2 q3w in accordance with clinician's usual practice). The primary endpoint is radiographic progression-free survival. Secondary endpoints include time on treatment holidays, safety, patient-reported outcomes, overall survival, health resource use, and cost associated with treatment. Enrolment commenced November 2021.

The results of this trial will generate data on the clinical utility of mGSTP1 as a novel biomarker to guide treatment de-escalation in metastatic CRPC.

Therapeutic advances in medical oncology. 2022 Apr 18*** epublish ***

Ciara Conduit, Blossom Mak, Wenjia Qu, Juliana Di Lulio, Ronan Burder, Matthias Bressel, Thomas Cusick, Haryana M Dhillon, Richard De Abreu Lourenço, Craig Underhill, Javier Torres, Megan Crumbaker, Florian Honeyball, Anthony Linton, Ray Allen, Ian D Davis, Susan J Clark, Lisa G Horvath, Kate L Mahon

Australian and New Zealand Urogenital and Prostate (ANZUP) Cancer Trials Group, Camperdown, NSW, Australia Personalised Oncology, Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia., Chris O'Brien Lifehouse, Camperdown, NSW, Australia Garvan Institute of Medical Research, Darlinghurst, NSW, Australia The University of Sydney, Sydney, NSW, Australia., Garvan Institute of Medical Research, Darlinghurst, NSW, Australia., Centre for Biostatistics and Clinical Trials (BaCT), Peter MacCallum Cancer Centre, Melbourne, VIC, Australia., Australian and New Zealand Urogenital and Prostate (ANZUP) Cancer Trials Group, Camperdown, NSW, Australia., Australian and New Zealand Urogenital and Prostate (ANZUP) Cancer Trials Group, Camperdown, NSW, Australia Centre for Medical Psychology and Evidence-Based Decision-Making, School of Psychology, Faculty of Science, The University of Sydney, Sydney, NSW, Australia Psycho-Oncology Cooperative Research Group, School of Psychology, Faculty of Science, The University of Sydney, Sydney, NSW, Australia., Centre for Health Economics Research and Evaluation, University of Technology Sydney, Sydney, NSW, Australia., Border Medical Oncology Research Unit, Albury Wodonga Regional Cancer Centre, Albury, NSW, Australia University of NSW Rural Clinical School, Albury, NSW, Australia., Goulburn Valley Health, Shepparton, VIC, Australia Rural Medical School, The University of Melbourne, Shepparton, VIC, Australia., Garvan Institute of Medical Research, Darlinghurst, NSW, Australia St. Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia The Kinghorn Cancer Centre, St. Vincent's Hospital Sydney, Darlinghurst, NSW, Australia., Dubbo Base Hospital, Dubbo, NSW, Australia School of Rural Health, The University of Sydney, Dubbo, NSW, Australia., The University of Sydney, Sydney, NSW, Australia Concord Cancer Centre, Concord Repatriation General Hospital, Concord, NSW, Australia., Australian and New Zealand Urogenital and Prostate (ANZUP) Cancer Trials Group, Camperdown, NSW, Australia Eastern Health Clinical School, Monash University, Box Hill, VIC, Australia Eastern Health, Box Hill, VIC, Australia., Garvan Institute of Medical Research, Darlinghurst, NSW, Australia UNSW Sydney, Sydney, NSW, Australia., Chris O'Brien Lifehouse, Camperdown, NSW, Australia Garvan Institute of Medical Research, Darlinghurst, Sydney, NSW, Australia The University of Sydney, Sydney, NSW, Australia Royal Prince Alfred Hospital, Camperdown, NSW, Australia., Chris O'Brien Lifehouse, 119-143 Missenden Rd, Camperdown, NSW 2050, Australia.