The aim of this study is to evaluate the efficacy of nab-paclitaxel (on days 1 and 8 of a 21-day cycle) compared to the standard regimen of docetaxel plus carboplatin, both combined with trastuzumab and pertuzumab, as neoadjuvant therapies for 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.