Reduced-dose Versus Conventional-dose Intensity-modulated Radiation Therapy for Locally Advanced Nasopharyngeal Carcinoma With Remission After Induction Chemotherapy and Immunotherapy

This study is testing whether patients with locally advanced nasopharyngeal cancer (cancer in the upper throat behind the nose) who respond very well to initial chemotherapy and immunotherapy can receive a lower dose of radiation therapy — with the aim of reducing side effects while maintaining the same cancer control. **You may be eligible if...** - You are between 18 and 70 years old - You have been diagnosed with stage III or IVa nasopharyngeal cancer confirmed by biopsy - You have completed 3 cycles of platinum-based chemotherapy combined with immunotherapy, and your tumor has responded very well (complete or partial response confirmed on MRI and scope) - Your Epstein-Barr virus (EBV) DNA levels have dropped to undetectable after induction chemotherapy - Your blood counts and organ function are in acceptable ranges **You may NOT be eligible if...** - Your cancer has spread to distant organs or recurred after prior treatment - Your tumor has not responded sufficiently to the initial chemotherapy and immunotherapy - Your EBV DNA levels remain elevated after induction treatment - You have poor overall health (ECOG score above 1) Talk to your doctor to see if this trial is right for you.