['her2 positive metastatic breast cancer']
['pyrotinib', 'lapatinib', 'capecitabine']

        Inclusion Criteria:

          -  Aged ≥18 and ≤70 years.

          -  ECOG performance status of 0 to 1.

          -  Life expectancy of more than 12 weeks.

          -  At least one measurable lesion exists.(RECIST 1.1).

          -  Histologically or cytologic confirmed HER2 positive advanced breast cancer which
             failed prior therapies.

          -  Required laboratory values including following parameters:

        ANC: ≥ 1.5 x 10^9/L;Platelet count: ≥ 100 x 10^9/L;Hemoglobin: ≥ 9.0 g/dL;Total bilirubin:
        ≤ 1.5 x upper limit of normal (ULN);ALT and AST: ≤ 1.5 x ULN;BUN and creatine clearance
        rate: ≥ 50 mL/min;LVEF: ≥ 50%;QTcF: < 470 ms for female and < 450 ms for male.

          -  Signed informed consent

        Exclusion Criteria:

          -  Received previous therapy with lapatinib, neratinib, pyrotinib or any other HER2
             directe tyrosine kinase inhibitor.

          -  Received previous therapy with capecitabine within 3 months.
      