Calcitriol Plus Dexamethasone in Treating Patients With Prostate Cancer That Has Not Responded to Hormone Therapy

OBJECTIVES: * Determine the maximum tolerated dose of calcitriol administered alone and in combination with dexamethasone in patients with hormone-refractory prostate cancer. * Determine the pharmacokinetics of calcitriol with and without dexamethasone in these patients. OUTLINE: This is a dose-escalation study of calcitriol. In the first stage of the study, cohorts of 3-6 patients receive escalating doses of oral calcitriol on days 1-3. Dose escalation continues until the maximum tolerated dose (MTD) is determined. In the second stage, patients receive escalating doses of oral calcitriol on days 1-3 and a fixed dose of oral dexamethasone on days 0-4. Treatment continues weekly in the absence of disease progression or unacceptable toxicity. Dose escalation continues until the MTD is determined. Six additional patients may receive calcitriol and dexamethasone at one dose level below the MTD determined in the second stage, to confirm the MTD. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity. PROJECTED ACCRUAL: Approximately 40 patients will be accrued for this study.