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

RATIONALE: Calcitriol may help prostate cancer cells become more like normal cells, and to grow and spread more slowly. Dexamethasone may help calcitriol work better by making tumor cells more sensitive to the drug. Giving calcitriol together with dexamethasone may be an effective treatment for prostate cancer that did not respond to hormone therapy .

PURPOSE: This phase II trial is studying how well giving calcitriol together with dexamethasone works in treating patients with prostate cancer that did not respond to hormone therapy.

OBJECTIVES:

* To investigate the response rate in patients with androgen-independent prostate cancer treated with calcitriol and dexamethasone.
* To evaluate the toxicity of high-dose calcitriol and dexamethasone in these patients.

OUTLINE: Patients receive oral dexamethasone once on days 1 and 2 and calcitriol IV over 1 hour on day 2. Treatment repeats weekly in the absence of disease progression or unacceptable toxicity.

Blood samples are collected at baseline and on days 2 and 3 to assess VDR and CYP24 expression in peripheral blood mononuclear cells.

Eligibility Criteria:
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