Cholecalciferol Supplement in Treating Patients With Localized Prostate Cancer Undergoing Observation

PRIMARY OBJECTIVES: I. To determine the prostate-specific antigen (PSA) response with oral high dose vitamin D3 supplementation (cholecalciferol) in patients with localized, histologically proven adenocarcinoma of the prostate who have not received any treatment for prostate cancer ever and have chosen expectant management. SECONDARY OBJECTIVES: I. To examine the pattern of response of PSA dynamics as well as the absolute change in PSA following vitamin D3 supplementation. II. Assess the toxicity of vitamin D3 supplementation in men with prostate cancer. TERTIARY OBJECTIVES: I. Track occurrence of infections, deep venous thrombosis, vascular events and falls in the study population. II. To evaluate relationship between cytochrome P450 family 24 (CYP24), 27B1, single-nucleotide polymorphism (SNPs) and serum 25(hydroxy \[OH\]) vitamin D response to oral D3 supplementation. OUTLINE: Patients are randomized to 1 of 2 treatment arms. ARM I: Patients receive cholecalciferol orally (PO) once daily (QD) for 9 months in the absence of disease progression or unacceptable toxicity. After a wash-out period of 3 months, patients cross-over to Arm II. ARM II: Patients receive placebo PO QD for 9 months in the absence of disease progression or unacceptable toxicity. After a wash-out period of 3 months, patients cross-over to Arm I. After completion of study treatment, patients are followed up for 30 days.