Pyrotinib Combined With Trastuzumab for Maintenance Therapy After First-line TH (P) Therapy for HER2+ABC

Inclusion Criteria: 1. Age: 18-70 years old, female; 2. Pathological examination confirmed HER-2 positive invasive breast cancer; Her2-positive is defined as \>10% of tumor cells with an immunohistochemical (IHC) score of 3+ or in situ hybridization (ISH) results as HER2 gene amplification. A positive HER2 should be confirmed by the pathology department of the participating center of this study.) Imaging examination confirmed recurrent/metastatic breast cancer; 3. Patients with recurrence or metastasis more than 1 year after trastuzumab treatment, or newly diagnosed stage IV breast cancer; 4. ECOG score is 0-1; 5. Expected survival ≥6 months; 6. Normal function of major organs; 7. 1\) Blood routine • ANC≥1.5×109/L; • PLT≥90×109/L; • Hb≥90 g/L; 2) Blood biochemistry • TBIL≤1.5×ULN; • ALT and AST≤2 x ULN; For patients with liver metastases, ALT and AST≤5× ULN; • BUN and Cr ≤ 1.5×ULN and creatinine removal rate ≥ 50 mL/min; 3) Heart color ultrasound • LVEF≥50%; 8. The researcher believes that the subject is likely to benefit; 9. Voluntarily participate in the study and sign the informed consent Exclusion Criteria: 1. Head MRI or head CT confirms the presence of brain metastases; 2. Have multiple factors affecting oral medication (history of gastrointestinal surgery, inability to swallow, chronic diarrhea, intestinal obstruction); 3. Study patients allergic to drugs and excipients; 4. Suffering from mental illness or psychotropic substance abuse, unable to cooperate; 5. Pregnant or lactating women; 6. Participated in clinical trials within 4 weeks; 7. Participants considered unsuitable for inclusion by the researchers.