Study of TS-1 as 2nd Line Treatment in Patients With Advanced Metastatic Breast Cancer

Inclusion Criteria:

* Age: 18-75 years old female.
* ECOG status: 0-2.
* Life expectancy of ≥ 3 months.
* Histologic or cytologic diagnosis of breast cancer.
* Progression after receiving one standard prior chemotherapy regimen for recurrent or metastatic lesion except an endocrine regimen.
* At least one measurable lesion of \>=2 cm (\>=1 cm on spiral CT scan)according to RECIST (v1.1).
* Adequate organ functions:

  * Hematopoietic: Hemoglobin ≥90g/L, Absolute neutrophil count ≥1.5×10\^9/L, Platelet count ≥80×10\^9/L.
  * Biochemistry: TBil ≤1.5 times upper limit of normal (ULN), AST and ALT ≤2.5× ULN(≤5x ULN if due to liver metastases), Creatinine ≤1.0×ULN and Creatinine clearance \>50 ml/min.
* Women with children potential must have negative pregnancy tests 7 days prior to enrollment and be willing to practice acceptable methods of birth control during the study and 8 weeks after last drug administered.
* Ability to take oral medication .
* Signed informed consent.

Exclusion Criteria:

* Pregnancy or lactation or no effective contraception in fertile patients.
* Prior treatment with 5-FU or drugs of same class(excluding patients that relapsed more than one year after adjuvant therapy).
* Less than 4 weeks since prior investigational agents.
* conditions impacting oral drug taking or absorption (e.g. inability to swallow, gastrointestinal resection, chronic diarrhea, intestinal obstruction).
* Organ invasion with rapid progression(e.g. lesions exceeding half of Liver or Lung).
* CNS or psychiatric disorders.
* Allergic to 5-FU.
* Only with bone metastases and no measurable lesions.
* Clinically significant heart diseases (e.g.congestive heart failure, ventricular arrhythmia, myocardial infarction) before enrollment.
* Serious peptic ulcer disease or digestive disorders.
* Bone marrow (Hemoglobin \<90g/dl, ANC \<1.5×10\^9/L, Platelet count \<75×10\^9/L).
* Renal function disorder (Creatinine \>1.0×ULN).
* Liver function disorder (TBil \>1.5×ULN).
* Uncontrolled brain metastases.
* Noncompliance with the study protocol.