Dynamic Risk-adapted EBV-DNA and MRI-guided De-concurrent Chemotherapy in Nasopharyngeal Carcinoma

Inclusion Criteria: * Age: 18 - 65 years old * Pathologically confirmed nasopharyngeal carcinoma, WHO type II or III non-keratinizing squamous cell carcinoma. * AJCC/UICC 9th edition stage II - III; excluding patients with T3N0M0 (only posterior pharyngeal lymph node metastasis) and T3N1M0. * Baseline plasma EBV-DNA \> 0, and able to complete dynamic monitoring according to the protocol. * ECOG 0 - 1. * Main organ functions meet the requirements: neutrophils ≥ 2.0×10\^9/L, platelets ≥ 100×10\^9/L, hemoglobin ≥ 90 g/L; ALT/AST ≤ 1.5×ULN, total bilirubin ≤ 1.5×ULN; creatinine clearance rate ≥ 60 mL/min. * Signed informed consent form, willing to complete the study according to the protocol. Exclusion Criteria: * Clinical or imaging examinations have confirmed distant metastasis. * Before the diagnosis of nasopharyngeal carcinoma, the patient had received chemotherapy, targeted therapy, or immunotherapy, and had a history of radiotherapy or surgery for head and neck tumors (except for diagnostic biopsies). * Has an active autoimmune disease, but the following conditions are excluded: type 1 diabetes, hypothyroidism receiving replacement therapy, and skin diseases that do not require systemic treatment (such as vitiligo, psoriasis, or alopecia). * Active hepatitis B with poor control of HBV DNA, active hepatitis C, HIV infection or uncontrolled infection. * Within 4 weeks before signing the informed consent form, the patient had used systemic glucocorticoids (equivalent to pre…