Assessing Combined SBRT in Breast Cancer Non-Responders to Neoadjuvant Chemotherapy

Inclusion Criteria: * Confirmed histologic diagnosis of invasive adenocarcinoma of the breast; * Stage T1-4N+M0 breast cancer (i.e., stages II and III); * Breast MRI showing no extracapsular extension of lymph node involvement; * The standard neoadjuvant chemotherapy regimen has been deemed ineffective after two cycles, with disease assessed as stable (SD) or progressive (PD) according to RECIST 1.1 criteria; * ECOG performance status score of 0-2; * Screening laboratory values must meet the following criteria: i. White blood cells (WBCs) ≥ 2000/μL ii. Absolute neutrophil count (ANC) ≥ 1500/μL iii. Platelets ≥ 100 x 103/μL iv. Hemoglobin ≥ 11.0 g/dL v. Serum creatinine ≤ 2 mg/dL (or glomerular filtration rate ≥ 40 ml/min) vi. AST ≤ 2.5 x upper limit of normal (ULN) vii. ALT ≤ 2.5 x ULN viii. Total bilirubin within normal limits (except subjects with Gilbert\'s syndrome, who must have total bilirubin \< 3.0 mg/dL) ix. INR ≤ 1.5 x ULN unless participant is receiving anticoagulant therapy as long as PT or aPTT is within therapeutic range of intended use of anticoagulant(s) x. Negative HIV screening test xi. Negative screening tests for Hepatitis B and Hepatitis C. Patients with positive results that do not indicate true active or chronic infection may enroll after discussion and consensus agreement by the treating physician and principal investigator. Exclusion Criteria: * Evidence of metastatic disease; * Known additional malignancy that is progressing or has required active treatment within the past 3 years； * Diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study drug； * Patients with other concurrent severe and/or uncontrolled medical conditions which could compromise participation in the study； * Pregnancy or breastfeeding.