All patients in this trial will receive the investigational (chemotherapy) drug at an optimal dose as determined by previous clinical trials. The investigational drug is given through a vein once every three weeks. This drug prevents tumor cells from dividing, so they may stop growing or die.
Inclusion Criteria: In order to be eligible for this trial you must: * Have a diagnosis of breast cancer that is now metastatic (meaning the cancer has spread beyond its original location) or a recurrence of the cancer in its original location that cannot be removed by surgery. * Have received previous treatment with anthracyclines (e.g. doxorubicin \[Adriamycin or Doxil\] or epirubicin \[Ellence\]), taxanes (paclitaxel \[Taxol or Abraxane\] or docetaxel \[Taxotere\]) and capecitabine (e.g. Xeloda) for your breast cancer and your doctor has determined that these treatments are no longer of benefit to you. * Be at least 18 years of age * Not be taking other treatments for your cancer at the time you enter the trial. * Not be pregnant * Additionally, there are other criteria for study entry that a doctor participating in this study will need to review in detail with you and clinical assessments may need to be performed (lab tests, CT scans). Exclusion Criteria: * None listed here. Can be discussed with your doctor.