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

This study is being done to answer the following question: can the chance of prostate cancer growing or spreading be lowered by adding a drug to the usual combination of drugs? This study would like to find out if this approach is better or worse than the usual approach for prostate cancer. The usual approach for patients who are not in a study is hormone treatment with Androgen Deprivation Therapy (ADT) and Androgen-Receptor Pathway Inhibitor (ARPI).

Inclusion Criteria: * Histologically/cytologically confirmed adenocarcinoma of the prostate or participants with a PSA \>100 ng/ml (100 ug/L) and radiographic evidence of metastatic disease at diagnosis. * Metastatic disease by conventional imaging (bone scan or CT and/or MRI or PSMA-PET scan at the time of ADT initiation. * PSA of ≥ 2.0 ng/ml (2.0 ug/L) prior to commencement of ADT (this refers to patients who have histologically/cytologically confirmed adenocarcinoma of the prostate) * Patients will have recovered from any treatment-related toxicities prior to enrollment (unless ≤ grade 1, irreversible, or considered by investigator as not clinically significant). * Patients may enroll with persistent toxicities attributable to ADT, including hot flushes and fatigue, of any grade, provided these toxicities are clinically stable, not rapidly worsening, and not considered by the Investigator to pose a safety risk or impair the patient's ability to comply with study procedures. Such toxicities do not need to resolve to Grade ≤1 prior to study entry. * Receipt of ADT for mCSPC for at least 6 months and no greater than 12 months (+/- 3 weeks) at time of enrollment. * Receipt of ARPI (e.g. abiraterone acetate, enzalutamide, apalutamide, or darolutamide) for at least 4 months (+/- 2 weeks) at time of enrollment * Patients may have had radiotherapy to prostatic bed and/or metastatic sites prior to enrollment. Potential trial participants should have recovered from radiotherapy-related toxicities prior to enrollment. * Serum testosterone \