Calcitriol and Dexamethasone in Treating Patients With Prostate Cancer That Did Not Respond to Hormone Therapy

DISEASE CHARACTERISTICS:

* History of androgen-independent prostate cancer

  * Evidence of rising PSA level (with or without new lesion by radiograph or physical examination), defined as follows:

    * PSA level \> 5 ng/mL and clearly rising on 2 measurements taken ≥ 2 weeks apart after androgen deprivation therapy (i.e., orchiectomy or luteinizing hormone-releasing hormone \[LHRH\] analogue) and antiandrogen withdrawal, if appropriate
  * PSA rising before and on the first value taken at 4 or 6 weeks after antiandrogen cessation is considered disease progression
* Measurable or evaluable disease as defined by any of the following:

  * Measurable or evaluable tumor masses by radiograph or physical examination
  * Evaluable PSA
* Concurrent LHRH analogue or diethylstilbestrol (DES) for testicular androgen suppression required if no prior bilateral orchiectomy

  * Patients receiving other monotherapy for testicular androgen suppression must switch to a LHRH analogue or DES ≥ 14 days prior to study entry

PATIENT CHARACTERISTICS:

* ECOG 0-2
* Life expectancy ≥ 12 weeks
* ANC ≥ 1,000/mm³
* Platelet count ≥ 75,000/mm³
* Hemoglobin \> 8.9 g/dL (transfusion or erythropoietin support allowed)
* Serum creatinine ≤ 1.8 mg/dL
* AST ≤ 4 times upper limit of normal (ULN)
* Total bilirubin ≤ 2.0 mg/dL
* Serum corrected calcium \< ULN
* No history of nephrolithiasis within the past 5 years
* No unstable, uncontrolled peptic ulcer disease, congestive heart failure, glaucoma, HIV, or diabetes

PRIOR CONCURRENT THERAPY:

* At least 28 days since prior androgen deprivation therapy (≥ 42 days for bicalutamide)

  * A 28-day washout period is not required for patients who have previously progressed despite antiandrogen withdrawal and who have resumed antiandrogens without reduction of PSA
* At least 14 days since prior radiotherapy
* At least 28 days since prior strontium 89
* At least 28 days since prior chemotherapy and/or investigational agents
* No concurrent medications or supplements that contain additional calcium (e.g., Tums)
* No concurrent radiotherapy for pain control or any other indication
* Concurrent bisphosphonates allowed provided dose/regimen is stable