Concurrent and Adjuvant PD1 Treatment Combined With Chemo-radiotherapy for High-risk Nasopharyngeal Carcinoma

Inclusion Criteria: 1. Histologically confirmed non-keratinizing nasopharyngeal carcinoma (differentiated or undifferentiated type, i.e., WHO type II or type III). 2. Staged as T4N0-2M0,T1-4N3M0 (stage IVa) at diagnosis (according to the 8th AJCC edition). 3. Staged as T1-3N1-2M0, T2-3N0M0 (stage II-III) with SD/PD according to RECIST criteria or EBV DNA of \>0 copies/mL after 3 cycles of GP induction chemotherapy. 4. Aged between 18-70 years. 5. Karnofsky scale (KPS)≥70. 6. Normal bone marrow function. 7. Normal liver and kidney function: 1. total bilirubin, AST and ALT levels of no more than 2.5 times the upper normal limit; 2. creatinine clearance rate of at least 60 mL/min or creatinine of no more than 1.5 times the upper normal limit. 8. Given written informed consent. Exclusion Criteria: 1. Histologically confirmed keratinized squamous cell carcinoma (WHO type I) or basal squamous cell carcinoma. 2. Recurrent or metastatic nasopharyngeal carcinoma. 3. Staged as II-III which is evaluated as PR or CR and EBV DNA of 0 copies/mL after 3 cycles of GP induction chemotherapy. 4. Has known allergy to large molecule protein products or any compound of study therapy. 5. Has known subjects with other malignant tumors. 6. Has any active autoimmune disease or history of autoimmune disease. 7. Has a history of psychiatric substance abuse, alcoholism, or drug addiction. 8. The laboratory examination value does not meet the relevant standards within 7 days before enrollment 9. Received a systematic glucocorticoid therapy within 4 weeks of the first dose of study medication. 10. Has a known history of active TB (bacillus tuberculosis) within 1 year; patients with adequately treated active TB with 1 year. 11. Prior therapy with a PD-1, anti-PD-Ligand 1 (PD-L1) or CTLA-4 agent. 12. Has active autoimmune disease (e.g., uveitis, enteritis, hepatitis, hypophysitis, nephritis, vasculitis, hyperthyroidism, and asthma requiring bronchodilator therapy). Patients with skin disease that doesn't require systemic treatment (e.g., vitiligo, psoriasis, or alopecia) will be allowed to enroll. 13. Has a known history of human immunodeficiency virus (HIV). 14. Has hepatitis B surface antigen (HBsAg) positive with HBV DNA copy number of ≥1000cps/ml or hepatitis C virus (HCV) antibody positive. 15. Has received a live vaccine within 4 weeks of planned start of study therapy. 16. Pregnancy or breast feeding.