Risk-Adapted Omission of Level Va Irradiation in Nasopharyngeal Carcinoma

Inclusion Criteria: 1. Pathologic diagnosis (pathologically confirmed by nasopharyngeal biopsy) was nasopharyngeal carcinoma; 2. No distant metastatic; 3. Eastern Cooperative Oncology Group (ECOG) score of 0 or 1; 4. Signing informed consent; 5. Follow up regularly and comply with test requirements. Exclusion Criteria: 1. Ipsilateral Level IIb involvement; 2. Ipsilateral Level III nodes involvement; 3. Ipsilateral positive lymph nodes below the cricoid cartilage (Level IV or Vb-c); 4. Disease progression during IMRT; 5. Previous malignancy or other concomitant malignant diseases; 6. The evaluation information of tumor efficacy can not be obtained; 7. Receive blind treatment in other clinical research; 8. Have or are suffering from other malignant tumors within 5 years (except non- melanoma skin cancer or pre-invasive cervical cancer); 9. Serious complications, such as uncontrolled hypertension, coronary heart disease, diabetes, heart failure, etc; 10. Active systemic infection; 11. No or limited capacity for civil conduct; 12. The patient has a physical or mental disorder, and the researcher considers that the patient is unable to fully or fully understand the possible complications of this study; 13. Pregnancy or lactation period;