CTV Delineation Based Solely on Geometric Expansion From GTV in Nasopharyngeal Carcinoma

Inclusion Criteria: 1. Pathologic diagnosis (pathologically confirmed by nasopharyngeal biopsy) was nasopharyngeal carcinoma; 2. No distant metastatic; 3. Patients with baseline MRI date of nasopharynx and neck, and completed the first course of treatment in our hospital; 4. Eastern Cooperative Oncology Group (ECOG) score of 0 or 1; 5. Signing informed consent; 6. Follow up regularly and comply with test requirements. Exclusion Criteria: 1. Disease progression during IMRT; 2. Previous malignancy or other concomitant malignant diseases; 3. The evaluation information of tumor efficacy can not be obtained; 4. Receive blind treatment in other clinical research; 5. Have or are suffering from other malignant tumors within 5 years (except non- melanoma skin cancer or pre-invasive cervical cancer); 6. Serious complications, such as uncontrolled hypertension, coronary heart disease, diabetes, heart failure, etc; 7. Active systemic infection; 8. No or limited capacity for civil conduct; 9. 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; 10. Pregnancy or lactation period;