This is a prospective, randomized Phase III trial of FLAC chemotherapy with GM-CSF versus PIXY321 in advanced breast cancer. The primary endpoints of this study will be the duration of thrombocytopenia and the time to recovery of platelets to 50,000/microliters. Other clinical endpoints will include the depth and duration of leukopenia, neutropenia, and anemia, the platelet and RBC transfusion requirements, and the number of documented instances of sepsis and hospitalizations for fever and neutropenia.