Inetetamab Combined With Pyrotinib and Chemotherapy in the Treatment of HER2 Positive Metastatic Breast Cancer

Inclusion Criteria: Subjects must meet all of the following conditions:

1. Adult female patients (age 18-70 years) with metastatic breast cancer confirmed bypathology or imaging;
2. Pathological diagnosis of HER-2 was positive (definition: immunohistochemical resultswere + + + or in situ hybridization results were positive);
3. Received trastuzumab treatment in the past;
4. the patients have received 1-3 treatments for metastatic breast cancer in the past;
5. According to RECIST 1.1, patients with at least one target lesion or simple bonemetastasis can be evaluated;
6. ECoG score of physical status was less than 2, and the expected survival time was notless than 3 months;
7. Prior treatment-related toxicity should be reduced to NCI CTCAE (version 5.0) ≤ 1degree (except for hair loss or other toxicity which is considered as no risk topatient's safety according to the investigator's judgment) 8）LVEF≥50%；

9. Sufficient functional reserve of bone marrow

1. White blood cell count (WBC) ≥ 3.0 × 10 ^ 9 / L,
2. Neutrophil count (ANC) ≥ 1.5 × 10 ^ 9 / L,
3. Platelet count (PLT) ≥ 100 × 10 ^ 9 / L 10) Previous treatment-related toxicity shouldbe relieved as NCI CTCAE (version 5.0) ≤ 1 degree, total bilirubin (TBIL) ≤ 1.5 ×upper limit of normal value (ULN), alanine aminotransferase (ALT / AST) ≤ 2.5 × ULN (liver metastasis patients ≤ 5xuln), serum creatinine ≤ 1.5 × ULN or creatinineclearance rate (CCR) ≥ 60 ml / min; 11) Be able to understand the research process,volunteer to participate in the study, and sign informed consent.

Exclusion Criteria: Subjects were not allowed to participate in the study if they had any of the followingconditions:

1. No trastuzumab treatment was received;
2. Have received more than 3 therapeutic regimens for metastatic breast cancer;
3. No treatment for metastatic breast cancer was received;
4. Patients who are known to be allergic to active or other components of the study drug.
5. They received radiotherapy, chemotherapy, endocrine therapy within 4 weeks beforeenrollment, or were participating in any clinical trials of intervention drugs;
6. Pregnant or lactating women, women of childbearing age who refused to take effectivecontraceptive measures during the study period.
7. Any other situation in which the researcher considers that the patient is not suitablefor the study may interfere with the concomitant diseases or conditions involved inthe study, or there are any serious medical barriers that may affect the safety of thesubjects (e.g., uncontrollable heart disease, hypertension, active or uncontrollableinfection, active hepatitis B virus infection)