DISEASE CHARACTERISTICS: Histologically or cytologically confirmed breast cancer Newly diagnosed or progressive metastatic disease with at least 1 metastatic target lesion No known clinical brain or leptomeningeal metastasis Phase I entry: Measurable and/or evaluable disease with an indicator lesion outside prior radiotherapy field Phase II entry: (closed as of 03/27/2000) Bidimensionally measurable disease with an indicator lesion outside prior radiotherapy field At least 1 x 1 cm on chest x-ray At least 2 x 2 cm on CT scan or ultrasound Skin lesion or node at least 1 x 1 cm No bone-only lesion Hormone receptor status: Not specified