Capecitabine Maintenance Therapy Following Capecitabine Combined With Docetaxel in Treatment of mBC

Inclusion Criteria: * Signed informed consent obtained prior to initiation of any study-specific procedures or treatment as confirmation of the patient's awareness and willingness to comply with the study requirements. * Female patients aged ≥ 18 years. * Histologically confirmed and documented HER2-negative metastatic breast cancer. * Previously untreated first-line chemotherapy. * Patients with at least one measurable lesion according to RECIST criteria at study entry. * Documented ER/PgR status. * Prior hormone therapy for metastatic disease is allowed but must stop before study entry. * KPS\>70. * Life expectancy of ≥12 weeks Exclusion Criteria: * Previous chemotherapy for metastatic breast cancer. * Prior adjuvant/neoadjuvant chemotherapy within 6 months prior to first study treatment administration. * Prior (radical)radiotherapy for the treatment of metastatic disease or major surgical procedure within 28 days prior to the first study treatment, * Inadequate bone marrow function: absolute neutrophil count (ANC): \<1.5 x 109/L, platelet count\<75 x 109/L or hemoglobin \<100g/L. * Inadequate liver or renal function, defined as: 1. Serum (total) bilirubin \>2 x the upper limit of normal (ULN) for the institution 2. AST/SGOT or ALT/SGPT \>2.5 x ULN (\>5 x ULN in patients with liver metastases) 3. ALP \>2.5 x ULN at baseline (\>5 x ULN in patients with liver metastases). 4. Serum creatinine\>140umol/L. * Pregnant or lactating females. * Her-2 positive (ICH +++ or FISH positive). * Symptomatic cerebral parenchyma and/or leptomeningeal metastases. * Other malignancy within the last 5 years, except for adequately treated carcinoma in situ of the cervix or squamous carcinoma of the skin, or adequately controlled limited basal cell skin cancer. * Pre-existing peripheral neuropathy ≥grade 1 according NCI CTCAE 4.0. * Mental disease or other conditions affecting on the compliance of patients. * Other serious disease or medical condition: 1. History of uncontrolled seizures, CNS disorders or psychiatric disability judged by the Investigator to be clinically significant precluding informed consent. 2. Congestive heart failure, or unstable angina, myocardial infarction within ≤6 months prior to the first study treatment, uncontrolled hypertension and high risk, uncontrolled arrhythmias. 3. Uncontrolled acute infection * Inability to take or absorption oral medications. * Concurrent or within 30 days using drugs of other clinical trials. * Previous treatments containing Capecitabine (whether adjuvant or palliative treatment). * Previous treatments containing docetaxel within 12 months. * Known hypersensitivity to any of the study treatments or excipients. * Any other conditions the research consider not appropriate to take part in the trial.