Vitamin D in Treating Patients With Prostate Cancer

RATIONALE: Vitamin D may be effective in treating patients with prostate cancer. PURPOSE: This randomized phase II trial is studying how well 4 different doses of vitamin D works in treating patients with prostate cancer.

OBJECTIVES: Primary * To examine the pattern of response of serum 25(OH) D3 levels following cholecalciferol (vitamin D3) supplementation at four different oral doses in patients with prostate cancer. Secondary * To examine the pattern of response of parathormone (PTH) following vitamin D3 supplementation in these patients. * To assess the toxicity of vitamin D3 supplementation in men with prostate cancer. Tertiary * To track occurrence of infections, deep vein thrombosis, vascular events, and falls in these patients. OUTLINE: Patients are randomized to 1 of 4 treatment arms. * Arm I: Patients receive 4,000 IU of oral cholecalciferol (vitamin D3) once daily. * Arm II: Patients receive 6,000 IU of vitamin D3 once daily. * Arm III: Patients receive 8,000 IU of vitamin D3 once daily. * Arm IV: Patients receive 10,000 IU of vitamin D3 once daily. Treatment in all arms continues for 6 months in the absence of disease progression or unacceptable toxicity.