RATIONALE: Calcitriol may cause prostate cancer cells to look more like normal cells, and to grow and spread more slowly. Drugs used in chemotherapy, such as mitoxantrone and prednisone, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing.

PURPOSE: This phase II trial is studying how well giving calcitriol together with mitoxantrone and prednisone works in treating patients with metastatic prostate cancer.

OBJECTIVES:

Primary

• Determine the prostate-specific antigen (PSA) response rate, defined as the fraction of patients with 50% reduction in PSA level over 3 weeks' time, in patients with androgen-independent metastatic prostate cancer treated with high-dose pulse calcitriol, mitoxantrone, and prednisone.

Secondary

• Determine the safety and tolerability of this regimen in these patients.

OUTLINE: This is a multicenter study.

Patients receive oral high dose pulse calcitriol on day 1, mitoxantrone IV on day 2, and oral prednisone on days 1-21. Treatment repeats every 21 days for up to 12 courses in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed periodically.

PROJECTED ACCRUAL: A total of 48 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed prostate cancer

  • Androgen-independent disease, defined as disease progression while on standard hormonal management, including antiandrogen withdrawal

    • Patients must continue primary hormonal therapy during study treatment

  • Regional or distant metastases

• Prostate-specific antigen > 5 ng/mL

• No brain metastases

PATIENT CHARACTERISTICS:

Age

• 18 to 100

Performance status

• ECOG 0-3

Life expectancy

• Not specified

Hematopoietic

• Adequate hematologic function

Hepatic

• Adequate hepatic function

Renal

• Adequate renal function
• No calcium-salt kidney stones within the past 5 years
• No hypercalcemia

Cardiovascular

• Adequate cardiac function
• No significant cardiac disease
• No atrial fibrillation

Other

• Fertile patients must use effective barrier contraception during and for 2 months after completion of study treatment
• No other serious medical illness
• No other active malignancy except nonmelanoma skin cancer

PRIOR CONCURRENT THERAPY:

Biologic therapy

• More than 28 days since prior biologic therapy

Chemotherapy

• No prior chemotherapy

Endocrine therapy

• See Disease Characteristics

Radiotherapy

• No prior strontium chloride Sr 89
• More than 28 days since prior radiotherapy
• More than 56 days since prior samarium Sm 153 lexidronam pentasodium

Surgery

• Prior prostatectomy and/or orchiectomy allowed

Other

• More than 28 days since prior investigational therapy