Inclusion Criteria

DISEASE CHARACTERISTICS: Histologically confirmed adenocarcinoma of the prostate or
metastatic carcinoma of presumptive prostate origin as manifest by the presence of
sclerotic bony metastases and a serum PSA level greater than the upper limit of normal
Radiologically proven progressive bone disease (e.g., new bone scan lesions, increased
uptake of isotope at previous sites of disease, and/or increasing bone pain) Hormone
refractory disease (i.e., disease progression or recurrence despite documented castrate
levels of serum testosterone achieved by bilateral orchiectomy or antiandrogen therapy)
Bone pain due to metastatic disease Patients must have achieved stable analgesia for at
least 7 days No uncontrolled epidural metastases

PATIENT CHARACTERISTICS: Age: Any age Performance status: ECOG 0-3 Life expectancy: At
least 3 months Hematopoietic: WBC at least 3,000/mm3 Absolute granulocyte count greater
than 1,500/mm3 Platelet count greater than 100,000/mm3 Hepatic: Bilirubin no greater than
3.15 mg/dL Renal: Creatinine less than 2.26 mg/dL Serum calcium no greater than 3.1 mmol/L
Cardiovascular: Patients with history of angina pectoris, previous cardiac infarction,
hypertension, or valvular or congenital heart disease must have baseline measurement of
LVEF exceeding 50% Other: No other malignancy within 5 years except nonmelanomatous skin
cancer No active infection or any other contraindication to chemotherapy with mitoxantrone
No spinal cord or nerve root compression No unstabilized impending pathological fractures

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: One previous
course of chemotherapy allowed No prior mitoxantrone or other anthracycline Endocrine
therapy: See Disease Characteristics At least 4 weeks since prior nonsteroidal
antiandrogens Radiotherapy: At least 4 weeks since prior radiotherapy At least 8 weeks
since prior strontium-89 or samarium-153 Surgery: Not specified Other: No prior
bisphosphonate therapy