The purpose of this study is to identify tumor cells in the bloodstream (Circulating Tumor Cells, CTC's) from patient's with locally advanced or metastatic (stage IV) breast cancer. Analyzing the tumor is helpful in guiding therapy; however, research has suggested that the number of tumor cells found in the bloodstream (CTC's) signifies more aggressive behavior and increased difficulty in eliminating the cancer. This research will help to develop better ways to treat breast cancer which could be tailored to a patient and may be adjusted to a patient's individual needs.

Up to 60 mL of blood will be collected from each patient at up to 6 time points. Samples will be delivered to the Bruce Laboratory (Palo Alto Research Center) for immunolabeling and FAST scanning. The FAST scanning will utilize CK+, CD45-and DAPI+ labeling as well as cell morphology confirmed by collaborating pathologists to select for CTC with the technology allowing for assessment of up to four additional protein expressions on the surface of CTC's. Additional samples at the proposed time points will be placed on ice and sent over to the Wang Laboratory for the purpose of extracting RNA/microRNA and proteins from CTC's for profiling and further analysis. Benefits are only to society, not the individual. Knowledge obtained from applying the two technologies may help with better selection of therapy, early detection of progression, possibly better diagnosis and development of targeted therapeutic agents in the future.

Inclusion Criteria:

• Patients must be > 18 years old.
• Patients are being treated for breast cancer at City of Hope (COH).

Brawerman Center-Outpatient clinics (City of Hope), Pasadena Satellite Office