Nab-Paclitaxel for Early HER2-positive Breast Cancer

Inclusion Criteria: Age: 18-70 years old. Clinical Tumor Stage: T2-T4d, or T1c with axillary lymph node positivity. Histologically confirmed HER2-positive invasive breast cancer: Note: HER2 positivity is defined as at least one assessment (either initial testing or central review) by the participating center's pathology department demonstrating tumor cells with immunohistochemistry (IHC) staining intensity of 3+ or confirmation by fluorescence in situ hybridization (FISH). Clinically measurable disease: Lesion measurable by ultrasound or MRI (optional) within 1 month prior to randomization. Adequate organ and bone marrow function within 1 month prior to chemotherapy initiation (no contraindications to chemotherapy): 1. Absolute neutrophil count (ANC) ≥ 2.0 × 10⁹/L 2. Hemoglobin ≥ 100 g/L 3. Platelet count ≥ 100 × 10⁹/L 4. Total bilirubin \< 1.5 × upper limit of normal (ULN) 5. Serum creatinine \< 1.5 × ULN 6. Aspartate aminotransferase (AST)/Alanine aminotransferase (ALT) \< 1.5 × ULN Cardiac function: Left ventricular ejection fraction (LVEF) ≥ 55% assessed by echocardiography. Women of childbearing potential: Negative serum pregnancy test within 14 days prior to randomization. Performance status: Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Informed consent: Provision of signed written informed consent. Exclusion Criteria: Stage IV (metastatic) breast cancer. Bilateral breast cancer. Prior systemic therapy or radiotherapy for the current breast cancer diagnosis, including chemotherapy, endocrine therapy, or targeted therapy. History of a second primary malignancy, except for adequately treated non-melanoma skin cancer or carcinoma in situ of the cervix. Major surgery unrelated to breast cancer within 4 weeks prior to enrollment, or incomplete recovery from prior major surgery. Significant cardiac disease or dysfunction, including but not limited to: 1. History of congestive heart failure or systolic dysfunction (LVEF \< 50%) 2. High-risk uncontrolled arrhythmias (e.g., atrial tachycardia, resting heart rate \> 100 bpm, clinically significant ventricular arrhythmia \[e.g., ventricular tachycardia\], or higher-grade atrioventricular block \[i.e., Mobitz II second-degree or third-degree heart block\]) 3. Angina pectoris requiring anti-anginal medication 4. Clinically significant valvular heart disease 5. Electrocardiogram (ECG) evidence of transmural myocardial infarction 6. Poorly controlled hypertension (systolic blood pressure \> 180 mmHg and/or diastolic blood pressure \> 100 mmHg) Presence of any other severe, uncontrolled medical condition that, in the investigator's judgment, constitutes a contraindication to chemotherapy. Known history of allergy to any component of the study drugs; patients with a history of immune deficiency diseases, including HIV positivity, or patients with other acquired or congenital immune deficiency diseases, or a history of organ transplantation.