PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent supportive colony-stimulating factors (e.g., filgrastim (G -CSF)) (Prophylactic treatment during the second step of phase I allowed) Chemotherapy: Phase I patients: At least 12 months since prior adjuvant chemotherapy Prior neoadjuvant chemotherapy allowed Prior cumulative dose of doxorubicin no greater than 300 mg/m2 Prior cumulative dose of epirubicin no greater than 500 mg/m2 If epirubicin dose level at least 90 mg/m2: Prior cumulative dose of doxorubicin no greater than 200 mg/m2 Prior cumulative dose of epirubicin no greater than 300 mg/m2 Phase II patients: (closed as of 03/27/2000) No prior neoadjuvant or adjuvant chemotherapy regimen other than cyclophosphamide, methotrexate, and fluorouracil, or doxorubicin and cyclophosphamide given for a maximum of 4 courses All patients: No prior chemotherapy for metastatic disease No prior taxanes Endocrine therapy: Prior hormonal therapy in the adjuvant and/or metastatic setting allowed if subsequent disease progression No more than 2 prior hormonal therapy regimens for metastatic disease No concurrent corticosteroids (except for premedication or hypersensitivity reaction) Radiotherapy: See Disease Characteristics At least 4 weeks since prior radiotherapy (unless single fractions for palliation) Concurrent local palliative radiotherapy for control of bone pain or for other reasons with no curative intent allowed Concurrent whole-brain radiotherapy for brain metastasis allowed No concurrent radiotherapy to sole measurable lesion Surgery: Not specified Other: No other concurrent investigational drugs or anticancer therapy No concurrent preventive IV antibiotics