Calcitriol and Zoledronate in Treating Patients With Progressive Prostate Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed prior localized adenocarcinoma of the prostate that has undergone definitive radiation or surgery and demonstrates progression biochemically with all of the following: * Baseline PSA at least 4 ng/mL * At least a 50% increase in PSA over at least 3 determinations taken at more than 2 week intervals * No radiographically evident disease * Neoadjuvant hormonal therapy prior to radical prostatectomy or radiotherapy allowed * Treatment in an intermittent approach allowed if off therapy for at least 12 weeks OR * Histologically confirmed androgen-independent adenocarcinoma of the prostate with all of the following: * Progression on primary hormonal treatment (e.g., orchiectomy, estrogen therapy, gonadotropin-releasing hormone analog with or without an antiandrogen) with either new osseous lesions in bone, a greater than 25% increase in bidimensionally measurable tumor mass, or rising PSA values (rising PSA on any 3 determinations taken at at least weekly intervals, to greater than 50% above baseline PSA) despite castrate levels of testosterone (no greater than 30 ng/mL) * If receiving antiandrogen as part of primary hormonal therapy, must meet criteria above for progression after discontinuation of antiandrogen * No change in hormonal therapy (including prednisone or dexamethasone) within the past 2 weeks * If no prior surgical orchiectomy, must continue on medical therapies to maintain castrate levels of testosterone * Prior chemotherapy, palliative radiotherapy, or radioisotope treatment allowed PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Karnofsky 70-100% Life expectancy: * At least 3 months Hematopoietic: * WBC at least 3,500/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * Bilirubin less than 2.0 mg/dL OR * SGOT less than 3 times upper limit of normal Renal: * Creatinine less than 1.5 mg/dL OR * Creatinine clearance at least 60 mL/min * No history of nephrolithiasis * Must have 2 functioning kidneys Cardiovascular: * No New York Heart Association class III or IV heart disease Pulmonary: * No severe debilitating pulmonary disease Metabolic: * No pre-existing endocrine or metabolic disorders that impact calcium regulatory axis including hypercalcemia (ionized serum calcium greater than 5.3 mg/dL or total calcium greater than 10.5 mg/dL) or hypercalciuria (greater than 300 mg urinary calcium/24 hours) Other: * No active secondary malignancy except nonmelanoma skin cancer * Must maintain low calcium diet (less than 800 mg calcium daily) * No uncontrolled serious active infection * No history of malabsorption disorders * No history of inflammatory bowel disease PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * See Disease Characteristics * At least 4 weeks since prior chemotherapy and recovered * No concurrent chemotherapy Endocrine therapy: * See Disease Characteristics * Recovered from prior endocrine therapy Radiotherapy: * See Disease Characteristics * At least 4 weeks since prior radiotherapy and recovered * No concurrent radiotherapy to sole measurable lesion Surgery: * See Disease Characteristics * Recovered from prior surgery * No concurrent surgery to sole measurable lesion Other: * No other concurrent cholecalciferol