• Female patients ≥ 18 years and ≤ 75 years old;

• Primary invasive breast cancer confirmed by histology;

• HER2 positive breast cancer (IHC 3+, or IHC 2+ and FISH positive); lymph node positive, except for T0; lymph node negative and tumor \>1cm, or tumor \> 0.5 cm and ≤ 1cm, and accompanied by any of the following high-risk factors: pathological grade 3, ER/PR negative, or \< 35 years old;

• Having received mastectomy or breast conserving surgery, and received sentinel lymph node biopsy or axillary lymph node dissection, and within 90 days from the breast surgery;

• With known ER/PR status of breast cancer;

• ECOG score 0-1;

• The patient's major organ functions meet all of the following requirements for blood tests:

‣ Neutrophil count (ANC) ≥ 1,500/mm3 (1.5×109/L);

⁃ Platelet count (PLT) ≥ 75,000/mm3 (75×109/L);

⁃ Hemoglobin (Hb) ≥ 8 g/dL (80 g/L);

⁃ Serum creatinine (SCr) ≤ 1.5 times the upper limit of normal (ULN) or creatinine clearance ≥ 60 mL/min;

⁃ Total bilirubin (TBIL) ≤ 1.5 times the upper limit of normal (ULN);

⁃ Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) level ≤ 2.5 times the upper limit of normal (ULN), patients with liver metastases should be ≤ 5×ULN.

∙ 9\. The participant voluntarily joins the study, signs the informed consent form, has good compliance, and cooperates with follow-ups.