Calcitriol in Preventing Prostate Cancer in Patients With Prostatic Intraepithelial Neoplasia

DISEASE CHARACTERISTICS: * Histologically confirmed high-grade prostatic intraepithelial neoplasia * Diagnosed within the past 6 months * No evidence of prostate cancer within the past 6 months * No evidence of palpable nodules on digital rectal exam * Prostate specific antigen ≤ 10 ng/mL within the past 3 months PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-1 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 Hepatic * SGOT and SGPT ≤ 1.5 times upper limit of normal Renal * No uncontrolled renal failure * No cancer-related hypercalcemia or kidney stones within the past 5 years Cardiovascular * No uncontrolled coronary artery disease * No uncontrolled congestive heart failure Other * Prior malignancy allowed provided patient was curatively treated and has been disease-free for an appropriate time period for the specific cancer * No known HIV positivity * No active infection * No major depression or suicidal ideation * No other condition that would preclude study compliance * No other uncontrolled medical condition PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * No prior chemotherapy for any malignancy Endocrine therapy * At least 2 weeks since prior and no concurrent finasteride (Prosear® or Propecia®) or other androgen suppressor * No concurrent corticosteroids Radiotherapy * Not specified Surgery * Not specified Other * At least 2 weeks since prior phenytoin or phenobarbital * At least 2 weeks since prior ketoconazole * No concurrent administration of any of the following: * Magnesium-containing antacids * Thiazide diuretics * Calcium supplements * Digoxin * Herbal supplements * Pharmacological doses of cholecalciferol (vitamin D) or its derivatives