A Study to Evaluate the Safety and Efficacy of Bevacizumab in Combination With Chemotherapy in Previously Treated Metastatic Breast Cancer (RIBBON 2)

Inclusion Criteria: * Signed informed consent form. * ≥ 18 years of age. * Histologically confirmed carcinoma of the breast with measurable or non-measurable metastatic disease that has progressed (patients with a history of brain metastasis are eligible for study participation \[USA only\], as long as their brain metastases have been treated and they have no evidence of progression or hemorrhage after treatment and no ongoing requirement for dexamethasone). * Progression of disease during or following administration of one (non-investigational) chemotherapy regimen administered in the first-line setting. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * For women of childbearing potential, use of an effective means of non-hormonal contraception. * Life expectancy ≥ 3 months. * Willingness and capacity to comply with study and follow-up procedures. Exclusion Criteria: * Prior hormonal therapy only as treatment for metastatic disease without chemotherapy. Patients must have received chemotherapy for their metastatic disease in the first-line setting. Hormone therapy alone is not allowed. * For subjects who have received prior anthracycline-based therapy, documentation of left ventricular ejection fraction \< 50% by either multiple gated acquisition (MUGA) or echocardiogram (ECHO). * Treatment with more than one prior cytotoxic regimen for metastatic breast cancer (MBC). * HER2-positive status (patients who have unknown HER2 status, and for whom determination of HER2 status is not possible, are eligible for this study). * Unknown estrogen receptor (ER) and progesterone receptor (PR) status. * Radiation therapy other than for palliation or brain metastasis, biologic therapy, or chemotherapy for MBC within 21 days prior to Day 0 (Day 1 of Cycle 1 of treatment). * Prior therapy with bevacizumab or other vascular endothelial growth factor (VEGF) pathway-targeted therapy. * Untreated brain metastasis. * Inadequately controlled hypertension. * Unstable angina. * New York Heart Association Grade II or greater congestive heart failure (CHF). * History of myocardial infarction within 6 months prior to Day 0 (the day of the first bevacizumab/placebo infusion). * History of stroke or transient ischemic attack within 6 months prior to Day 0. * Clinically significant peripheral vascular disease. * Evidence of bleeding diathesis or coagulopathy. * Major surgical procedure, open biopsy, or significant traumatic injury within 28 days prior to Day 0; anticipation of need for major elective surgical procedure during the study. * Minor surgical procedures, fine-needle aspirations, or core biopsies within 7 days prior to Day 0. * History of abdominal fistula, gastrointestinal perforation, or intra-abdominal abscess within 6 months prior to Day 0. * Serious, non-healing wound, ulcer, or bone fracture. * History of anaphylactic reaction to monoclonal antibody therapy not controlled with treatment premedication. * History of other malignancies within 5 years of Day 0, except for tumors with a negligible risk for metastasis or death, such as adequately controlled basal cell carcinoma or squamous cell carcinoma of the skin or carcinoma in situ of the cervix. * inadequate organ function. * Pregnancy (positive serum pregnancy test) or lactation. * Any other diseases, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or renders the subject at high risk from treatment complications.