The purpose of this study is to investigate whether reducing both the dose and the irradiated volume of cervical prophylactic irradiation in patients with nasopharyngeal cancer can maintain efficacy while decreasing toxicity. This will be achieved through a comparison of standard cervical prophylactic irradiation with a reduced-dose and reduced-volume approach.

Patients with non-metastatic nasopharyngeal cancer who are candidates for receiving definitive IMRT are randomly assigned to receive either standard cervical prophylactic irradiation or a reduced-dose and reduced-volume approach. The standard arm receives the conventional dose and volume of irradiation, while the experimental arm receives a lower dose and a smaller irradiated volume. Both groups will undergo intensity-modulated radiotherapy (IMRT) to the primary tumor and involved lymph nodes. The primary endpoint of this study is regional-control (RC), and secondary endpoints include overall survival (OS), local control (LC), distant metastasis-free survival (DMFS), and toxicity. All efficacy analyses will be conducted in the intention-to-treat population, and the safety population will include only patients who receive their randomly assigned treatment.

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;