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