Reducing Dose and Irradiated Volume in Cervical Prophylactic Irradiation for Nasopharyngeal Cancer

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;