Creatine Supplementation and Resistance Training to Preserve Muscle Mass and Attenuate Cancer Progression

Inclusion Criteria: * Subject age ≥ 18 years old. * Metastatic castration-sensitive prostate cancer patients who have not met criteria for disease progression (per Prostate Cancer Working Group guidelines) on current systemic therapy * Currently treated with surgical castration or medical castration with Gonadotropin-releasing hormone (GnRH) agonists/antagonists, and/or an androgen receptor pathway inhibitor (ARPI)) aka novel hormone therapy (e.g., abiraterone, enzalutamide, apalutamide, darolutamide). Must have started the current regimen at least 12 weeks prior to enrollment. * Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 2 * Not currently adhering to national physical activity guidelines for resistance training, as defined as participating in structured resistance training (e.g., time set aside in your day to workout) ≥ two days per week. * Regular access to an electronic device with internet service and ability for video calls (e.g., computer, smart phone, iPad, tablet, etc). * Access to an active MyChart account or the willingness to create an account for the purposes of the trial. * Willingness to engage in a home-based resistance exercise program two days per week. * Willingness to take creatine monohydrate supplementation or placebo for the duration of the 52 week trial and to avoid taking additional creatine-containing supplementation or other nutritional supplementation during the study period. * Willingness to complete and submit weekly supplementation logs to study personnel throughout the duration of the 52-week study via email, text, in person, or verbally verified over the phone. * Willingness to complete three in-person assessment sessions (baseline, 24-, and 52-weeks). * Able to provide informed consent and willing to sign an approved consent form that conforms to federal and institutional guidelines. Exclusion Criteria: * Treatment with cytotoxic chemotherapy within 12 weeks prior to enrollment. * Estimated Glomerular Filtration Rate (eGFR) \< 30 ml/min/1.73m2. * ECOG Performance Status ≥ 3