Radiotherapy Alone Versus Concurrent Chemo-radiotherapy for Nasopharyngeal Carcincoma Patients With Undectable EBV DNA After One Cylce Neoadjuvant Chemotherpy

Inclusion Criteria: 1. Patients with newly histologically confirmed non-keratinizing nasopharyngeal carcinoma, type of WHO II or III. 2. Age 18-70 years. 3. Clinical stage III-IVa (based on the 8th American Joint Committee on Cancer\[AJCC\] edition). 4. Patients with detectable pre-treatment plasma EBV DNA but undetectable EBV DNA after one cycle neoadjuvant and no EBV DNA rebound during the second and third cycle. 5. ECOG (Eastern Cooperative Oncology Group) score: 0-1 6. Hemoglobin (HGB) ≥90 g/L, white blood cell (WBC) ≥4×109 /L, platelet (PLT) ≥100×109 /L. 7. Liver function: Alanine transaminase(ALT), Aspartate aminotransferase(AST)\< 1.5 times the upper limit of normal value (ULN), total bilirubin \<1.0×ULN. 8. Renal function: serum creatinine \<1×ULN. 9. Patients must sign informed consent and be willing and able to comply with the requirements of visits, treatment, laboratory tests and other research requirements stipulated in the research schedule. Exclusion Criteria: 1. Histologically confirmed keratinizing squamous cell carcinoma (WHO I) 2. Suffered from other malignant tumors (except the cure of basal cell carcinoma or uterine cervical carcinoma in situ) previously. 3. Receiving radiotherapy or chemotherapy or targeted therapy previously 4. Women of child-bearing potential who are pregnant or breastfeeding because of the potentially dangerous effects of the preparative chemotherapy on the fetus or infant. 5. Patients with significantly lower heart, liver, lung, kidney and bone marrow function. 6. Severe, uncontrolled medical conditions and infections. 7. At the same time using other test drugs or in other clinical trials. 8. Refusal or inability to sign informed consent to participate in the trial. 9. Emotional disturbance or mental illness, no civil capacity or limited capacity for civil conduct