The goal of this clinical trial is to assess whether the addition of preoperative stereotactic body radiation therapy (SBRT) can improve pathological complete response (pCR) rates and safety in breast cancer patients who do not respond to initial neoadjuvant chemotherapy. The main questions it aims to answer are:
* Can the combination of SBRT with chemotherapy increase pCR rates in non-responders to initial neoadjuvant chemotherapy? * Does the addition of SBRT to chemotherapy have acceptable safety and tolerability profiles?
Participants in this trial will be early or locally advanced breast cancer patients who have shown no response to two cycles of standard neoadjuvant chemotherapy. They will be randomly assigned to either continue with the standard chemotherapy (control group) or receive SBRT in addition to continuing the standard chemotherapy (intervention group). The primary outcome measures will be pCR rate and breast conservation rate. Secondary outcomes will include 3-year local progression-free survival, overall survival, surgical complications, and treatment toxicities.
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;
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；