Serplulimab Plus Chemotherapy for Early-stage HR+/HER2- Breast Cancer

Inclusion Criteria Patients must meet all of the following criteria to be eligible: Age: ≥18 years old. Clinical-pathological confirmation: cT2-cT4 breast cancer, or cT1c with axillary lymph node metastasis. Histopathologically confirmed HR+/HER2- invasive breast cancer: ER and/or PR positive (IHC nuclear staining ≥1%). HER2-negative (IHC 0 or 1+ without FISH testing, or IHC 2+ with FISH-negative amplification). Ki67 ≥20%. Clinically measurable lesions: Measurable lesions confirmed by ultrasound, mammography, or MRI (optional) within 1 month prior to randomization. Adequate organ and bone marrow function (within 1 month prior to chemotherapy): Absolute neutrophil count (ANC) ≥2.0 × 10\^9/L. Hemoglobin ≥90 g/L. Platelet count ≥100 × 10\^9/L. Total bilirubin \<1.5 × ULN (upper limit of normal). Creatinine \<1.5 × ULN. AST/ALT \<1.5 × ULN. Cardiac function: Left ventricular ejection fraction (LVEF) ≥55% by echocardiography. Reproductive status: Women of childbearing potential must have a negative serum pregnancy test within 14 days prior to randomization. ECOG performance status: ≤1. Informed consent: Signed written informed consent. Exclusion Criteria Patients meeting any of the following criteria will be excluded: Evidence of metastatic breast cancer: Prior systemic therapy: Chemotherapy, endocrine therapy, targeted therapy, or radiotherapy for the current breast cancer. Second primary malignancy, except: Adequately treated non-melanoma skin cancer. Prior immunotherapy: Treatment with anti-PD-1, anti-PD-L1, anti-PD-L2, or other immune checkpoint inhibitors. Immune-related conditions: Diagnosed immunodeficiency or active autoimmune disease. Severe cardiopulmonary disease: Uncontrolled or clinically significant. Active hepatitis B or C. Pregnancy or lactation: Pregnant or breastfeeding women. Other contraindications: Severe uncontrolled comorbidities deemed by investigators to contraindicate chemotherapy or PD-1 inhibitor therapy.