This prospective, randomized comparative study aims to evaluate the clinical outcomes and safety of response-adapted de-escalation of Regional Nodal Irradiation (RNI) in initially node-positive (cN1) breast cancer patients who achieved a pathological nodal complete response (pCR) following neoadjuvant systemic therapy. Patients will be randomized into two arms: Arm A (Experimental Arm) which omits regional nodal irradiation, and Arm B (Control Arm) which receives standard regional nodal irradiation.
