The objective of this phase II study is to evaluate efficacy and safety of avastin plus modified FOLFOX6 regimen in HER-2 negative metastatic breast cancer patients. Fifty-five patients will be enrolled into this study.

Anthracyclines and taxanes are the most frequently used agents for breast cancer,both in adjuvant and in first-line metastatic settings.For the patients who do not respond or relapse early after the administration of a taxane or anthracycline regimen,it is clearly needed to explore new combinations and schedules of drugs.Oxaliplatin has shown very promising activity in MBC either in monotherapy or in combination with 5-fluorouracil(5-FU) with or without leucovorin (LV). Avastin is a target therapy with proven efficacy in the treatment of MBC. Avastin plus FOLFOX regimen showed synergetic effet and been used as the standard trial in metastatic colorectal cancer patients. Based on the above reason, we initiate this phase II study to evaluate efficacy and safety of avastin plus modified FOLFOX6 regimen in HER-2 negative metastatic breast cancer patients.

Inclusion Criteria:

1. age>=18years
2. Eastern Cooperative Oncology Group (ECOG) performance status (PS) <=2 and a life expectancy >= 12 weeks;
3. histological-proven, HER-2 negative measurable stage IV disease;
4. exposure to anthracyclines, taxanes either in the neoadjuvant/adjuvant or in the metastatic setting and had documented disease progression after the firstline or secondline treatment
5. Patients previously treated with radiotherapy were eligible for the study, provided that measurable disease existed outside the radiation field.
6. At least 3 weeks from the prior chemotherapy or radiotherapy. At least 2 weeks from the prior endocrine therapy.

Exclusion Criteria:

1. Patients with active infection or other serious underlying medical conditions
2. Patients had prior treatment with 5-FU infusion and/or oxaliplatin therapy
3. Inadequate bone marrow, liver, renal, medullary, and cardiac functions
4. Evidence of spinal cord compression or brain metastasis
5. History of another malignancy within the last five years except cured basal cell carcinoma of skin and carcinoma in-situ of uterine cervix or a contralateral breast cancer
6. Pregnant or lactating women
7. Serious uncontrolled intercurrent infection
8. History or evidence of inherited bleeding diathesis or coagulopathy with the risk of bleeding
9. Serious non-bleeding wound, peptic ulcer or bone fracture
10. Prior dihypopyrimidine dehydrogenase deficiency
11. Hypersensitivity to Chinese hamster ovary cell products or other recombinant human or humanlised antibodies