Nab-paclitaxel in Combination With Pyrotinib in Postoperative Adjuvant Therapy for HER2-positive Breast Cancer

Inclusion Criteria: * Enrollment subjects must have a pathological diagnosis of HER2-positive primary invasive breast cancer with an immunohistochemistry (IHC) score of 3 +, or 2 + and HER2 gene amplification by in situ hybridization (ISH) (ratio of HER2/CEP17 ≥ 2.0). * The invasive tumor had to measure no more than 3cm and with histologically confirmed lymph node-negative or one lymph node micrometastasis (T ≤ 3 cm, N0/N1mi, M0). * Tumor should has known ER/PR hormone receptor status. * All patients must be women above18 years old with Eastern Cooperative Oncology Group score 0 to 1. * Adequate hematopoietic function and organ function as defined as follows: neutrophil count ≥ 1.5 x 109/L; Platelet count ≥ 90 × 109/L; Hemoglobin ≥ 90 g/L; total bilirubin ≤ 1.5 × ULN; alanine transaminase (ALT) and aspartate transaminase (AST) ≤ 3 × ULN; serum creatinine Cr ≤ 1.5 × ULN and creatinine clearance ≥ 50 mL/min (Cockcroft-Gault formula). * left ventricular ejection fraction (LVEF) ≥ 50% and Electrocardiogram Fridericia-corrected QT interval (QTcF) ≤ 480 ms. * Provide written informed consent. Exclusion Criteria: * Clinical or radiologic evidence of local or regional recurrence of disease or metastatic disease prior to or at the time of study entry. * Previous treatment with chemotherapeutic drugs, or tyrosine kinase inhibitors targeting HER2 (lapatinib, neratinib or pyrotinib, etc.). * Other malignancies within the past 5 years, excluding cured cervical carcinoma in situ, cutaneous basal cell carcinoma, or cutaneous squamous cell carcinoma. * Inability to swallow, chronic diarrhea, or intestinal obstruction. * Known to be allergic to the drug components. * Have a history of immunodeficiency, including HIV positive, HCV positive, active viral hepatitis B or other immunodeficiency diseases. * Have a history of organ transplantation. * Pregnant, lactating female patients, or female patients who are unwilling to take effective contraceptive. * Any heart disease, including: (1) arrhythmia; (2) myocardial infarction; (3) heart failure. * Any other concomitant diseases assessed by investigator as unsuitable for study. * Previous history of definite neurological or psychiatric disorders. * Concomitant use of CYP3A4 inhibitors or inducers or drugs that prolong the QT interval.