Calcitriol and Dexamethasone 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.

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