Testosterone-Informed De-Escalation in Metastatic Prostate Cancer (TIDE PC)

The purpose of this study is to use androgen deprivation therapy (ADT) intermittently in hopes of reducing side effects from ADT and reducing unnecessary dosing of ADT in adult men with a prolonged response to frontline therapy for metastatic hormone-sensitive prostate cancer (mHSPC). The primary aim is to determine the cumulative incidence of participants who experience prostate-specific antigen (PSA) relapse, clinical relapse, or death in the 18-month trial period. The study will investigate the effects of holding (stopping and restarting as needed) ADT in the participants to monitor time to non-castrate testosterone, quality of life, and outcomes when ADT is only restarted when testosterone is above the castration-level threshold. Androgen receptor pathway inhibitor (ARPI) will be continued for additional safety. PSA will be monitored throughout to ensure there is no rise. Additionally, quality of life will be monitored throughout to determine whether greater time between ADT doses leads to improvement in side effects. Participants will: * See their provider every 3 months * Check Testosterone and PSA levels every 3 months * Hold androgen deprivation therapy (ADT) when testosterone remains \<50 ng/dL and resume ADT when testosterone is ≥50 ng/dL * Continue to take androgen receptor pathway inhibitor (ARPI) throughout the trial * Complete Functional Assessment of Cancer Therapy-Prostate (FACT-P) and Hot Flash Related Daily Interference Scale (HFRDIS) surveys * Undergo imaging throughout the study as clinically indicated, which is consistent with the standard of care