Blood Levels of Tumor Cells in Predicting Response in Patients Receiving First-Line Chemotherapy for Stage IV Breast Cancer

OBJECTIVES: Primary * Predict the overall and progression-free survival of patients with stage IV breast cancer by measuring the rate of circulating tumor cells (CTC) before the second course of chemotherapy. Secondary * Predict overall and progression-free survival of these patients by measuring the rate of CTC before the start of chemotherapy, at the first tumor evaluation, and after 2-3 courses of chemotherapy. * Correlate the detection of CTC with tumor markers, clinical response, and radiological response. * Study the changing status of HER-2 in CTC in patients receiving trastuzmab (Herceptin®). OUTLINE: This is a multicenter study. Blood samples are collected at baseline, before the second course of chemotherapy, before the third or fourth course of chemotherapy, and when progressive disease is diagnosed (before second-line treatment is initiated). Circulating tumor cells from the blood samples are examined by immunofluorescence. Patients are followed periodically for up to 3 months.