We are trying to develop better ways to detect when cancer therapies are working.

Inclusion Criteria:

1.Females at least 18 years of age 2 Diagnosis of metastatic breast cancer 3.ECOG Score of 0-2 4.Treating oncologist has decided to initiate any new systemic therapy with emphasis on recruiting patients commencing a taxane-based regimen. Taxine-based therapy may be docetaxel or paclitaxel, and it can be given on any schedule,including weekly or every 3 weeks. Other treatment can include non-taxane chemotherapy or trastuzumab-with or without other therapy.

5.Patient is willing to return for one or more additional ~18 mL blood draw (s) at 24-48-, and /or 72 hours and ~3-4 weeks after the initiation of therapy.At a minimum, patients must donate blood at baseline, one intermediate interval (24, 48, 72 hr) and at ~3-4 weeks 6.Signed Informed Consent Form

-

Exclusion Criteria:

Patient is unable and unwilling to provide a blood specimen at a minimum of one of the intermediate blood draw time points at 24, 48, or 72 hours -

women with metastatic breast cancer