Comparative Analysis of Immunological Responses to Vitamin D Replacement Therapy in Black and West African Men Diagnosed With Prostate Cancer: Elucidating Differential Effects on Immune Function Between Patients With Localized Disease and Those With Metastatic Progression

This study is testing whether fixing vitamin D deficiency in Black/West African men with prostate cancer can strengthen their immune system, improve quality of life, and even slow cancer progression compared to those who remain deficient. Key ideas being tested: 1. More than half of Black/West African prostate cancer patients don't have enough vitamin D. 2. Low vitamin D weakens immune cell function and affects quality of life, but these problems improve after 8 weeks of vitamin D supplements. 3. Immune cell function differs between patients with advanced/recurrent prostate cancer and those with localized disease. 4. Patients with advanced disease who show stronger immune responses after vitamin D correction may live longer without their PSA levels rising (a marker of cancer progression). 5. Immune cell function in Black/West African patients is different from that in Black/African American patients, and this will be checked by comparing data with a parallel Mayo Clinic study. Overall goals: 1 . Measure how widespread vitamin D deficiency is in Black/West African prostate cancer patients. 2\. Understand how vitamin D levels affect immunity and quality of life. 3. Compare immune function between different groups (localized vs. advanced disease, West African vs. African American patients). 4 . See if vitamin D replacement improves both patient well-being and cancer outcomes. Study Flow 1\. Recruitment \& Consent: Patients with prostate cancer (localized or advanced) are invited and give written consent. 2 . Initial Blood Test (10 mL): Check vitamin D and calcium levels. 3. Eligibility: If vitamin D is low (\<30 ng/mL), patients join the treatment phase. 4\. Baseline Testing (50 mL blood + QOL survey): Immune function measured; quality of life survey completed; virtual doctor consult. 5\. Treatment (8 weeks): Daily vitamin D3 pills (2000 IU, free); patients keep a medication diary. 6\. Midpoint Check (Week 4): Phone call to check side effects and compliance