PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent immunotherapy Concurrent hematopoietic growth factor allowed Chemotherapy: No prior chemotherapy for metastatic breast cancer No concurrent chemotherapy Endocrine therapy: No prior hormonal therapy for metastatic breast cancer (except tamoxifen) No concurrent supplemental estrogen or progesterone At least 3 weeks since prior estrogen replacement therapy No other concurrent hormone therapy Radiotherapy: At least 2 weeks since prior radiotherapy Surgery: Not specified Other: At least 4 weeks since prior use of other investigational agents Concurrent bisphosphonate therapy allowed No other concurrent investigational agent