It is a phase III trial to explore the efficacy and safety of metronomic chemotherapy with Capecitabine versus intermittent Capecitabine as maintenance therapy following first-line Capecitabine plus Docetaxel chemotherapy in treatment of HER2-negative metastatic breast cancer(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.