Docetaxel to Androgen Receptor Pathway Inhibitors in Patients With Metastatic Castration Sensitive Prostate Cancer and Suboptimal PSA Response

Inclusion Criteria: * Histologically/cytologically confirmed adenocarcinoma of the prostate * Metastatic disease by conventional imaging * PSA of ≥5.0 ng/ml (5.0 ug/L) prior to commencement of ADT * Receipt of ADT for mCSPC for at least 6 months and no greater than 12 months at time of enrollment. * Receipt of ARPI (e.g. abiraterone acetate, enzalutamide, apalutamide, or darolutamide) for at least 4 months at time of enrollment * Potential trial participants should have recovered from clinically significant adverse events of their most recent therapy/intervention prior to enrollment. * Serum testosterone \<1.7 nmol/L or 50 ng/dL. * PSA ≥ 0.2 ng/ml (0.2 ug/L) within 14 days of enrollment. If there is any rise in PSA since starting ADT and achieving castrate-level testosterone, PSA must be repeated and must not fulfill ineligibility criteria 4.2.1. * Candidate for docetaxel chemotherapy * ECOG Performance Status (PS) 0 to 2. * Adequate organ and marrow function measured within 14 days prior to enrollment. * Participant consent must be appropriately obtained in accordance with applicable local and regulatory requirements. Each participant must sign a consent form prior to enrollment in the trial to document their willingness to participate. * Participants must be accessible for treatment and follow-up. Investigators must assure themselves the participants enrolled on this trial will be available for complete documentation of the treatment, adverse events, and follow-up. * In ac…