PD-1 Combined With Intensity Modulated Radiation Therapy in the Treatment of Intermediate-risk Nasopharyngeal Carcinoma

Inclusion Criteria: * Newly diagnosed patients who have not received radiotherapy or chemotherapy * Pathologically diagnosed as non-keratinizing nasopharyngeal carcinoma (differentiated or undifferentiated, WHO classification type II or type III). * T2-3N0 or T1-2N1 stage and EBV-DNA≤4000 copy/ml (AJCC 8th version) and EBV-DNA≤4000copies/ml * Male or non-pregnant female * Age between 18 and 65 * Eastern Cooperative Oncology Group（ECOG）score of 0-1. * Hemoglobin (HGB) ≥90 g/L, white blood cell (WBC) ≥4×109/L, platelet (PLT) ≥100×109/L. * Liver function: Alanine aminotransferase (ALT), aspartate aminotransferase (AST) \<2.0 times the upper limit of normal (ULN); total bilirubin \<2.0×ULN. * Renal function: creatinine clearance rate ≥60ml/min or serum creatinine \<1.5×ULN. * The patient has signed the informed consent Exclusion Criteria: * The pathology is keratinizing squamous cell carcinoma (WHO classification is type I). * Patients with recurrence and distant metastasis. * Patients who have undergone radiotherapy or chemotherapy. * Active hepatitis B (HBV-DNA≥500). * Patients with autoimmune diseases. * Patients with HIV infection. * At the same time suffering from other uncontrolled serious diseases. * Persons with abnormal functions of the heart, brain, lungs and other important organs. * Age\> 65 years. * pregnancy or breast feeding. * Persons with personality or mental illness, without or with limited capacity for civil conduct