The primary objective of this study is to evaluate the efficacy and tolerability of sequential use of vinorelbine and capecitabine as first line therapy in patients with MBC.

The administration of vinorelbine and capecitabine had been implied to be quite useful in metastatic breast cancer. This study was designed to explore whether sequential and simultaneous use of vinorelbine and capecitabine have similar efficacy and whether the sequential way has better tolerability.

Inclusion Criteria:

• Signed informed consent.
• Female, ≥ 18 and ≤ 70 years.
• Histologically confirmed invasive breast cancer.
• Metastatic breast cancer.
• ECOG Performance Status of 0 to 2.
• Life expectancy of more than 3 months.
• Subject must have adequate organ function.
• Normal laboratory values: hemoglobin > 90g/dl, neutrophils > 1.5×10^9/L, platelets > 80×10^9/L, serum creatinine < 1.5×upper limit of normal (ULN), serum bilirubin < 1.5×ULN, ALT and AST < 2.5×ULN.
• Negative serum pregnancy test for women with childbearing potential.
• Good conditions for infusion and willing to have phlebotomy throughout whole study.
• Have ceased anti-tumor treatments including endocrinotherapy and bio-targeted therapy for more than 28 days.
• Have at least one target lesion according to the Response Evaluation Criteria in Solid Tumors (RECIST) criteria.

Exclusion Criteria:

• Pregnant or lactating females
• History of other malignancy. However, subjects who have been disease-free for 5 years, or subjects with a history of completely resected non-melanoma skin cancer or successfully treated in situ carcinoma are eligible
• Concurrent disease or condition that would make the subject inappropriate for study participation, or any serious medical disorder that would interfere with the subject's safety
• Active or uncontrolled infection
• Known history of uncontrolled or symptomatic angina, arrhythmias, or congestive heart failure
• Concomitant with brain metastases
• Have received chemotherapy after metastasis