This is an randomized, controlled, phase 3 clinical trial. The purpose of this study is to evaluate whether medial group retropharyngeal node （MRLN） sparing could reduce the incidence of radiation-caused dysphagia and improve patients' quality of life without compromising survival rate.

In this study, patients with non-keratinizing stage T1-4 N0-3 M0 NPC(UICC/AJCC 8th edition), except for patients with MRLN metastasis, are randomly assigned to receive MRLN sparing or prophylactic irradiation . Patients in MRLN sparing group will not routinely receive MRLN irradiation to 56Gy/33Fr; while patients in MRLN prophylactic irradiation group will always receive MRLN irradiation to 56Gy/33Fr. Our primary endpoint is local relapse-free survival (LRFS). Secondary end points include overall survival (OS), incidence of out-field recurrence rate, toxic effects, and quality of life (QOL).All efficacy analyses are conducted in the intention-to treat population, and the safety population include only patients who receive their randomly assigned treatment.

Inclusion Criteria:

1. Patients without medial group retropharyngeal node metastasis;
2. Patients with newly histologically confirmed non-keratinizing (according to WHO histologically type);
3. Tumor staged as T1-4N0-3(according to the 8th AJCC edition);
4. No evidence of distant metastasis (M0);
5. Satisfactory performance status: Karnofsky scale (KPS) ≥ 70;
6. Patients must be informed of the investigational nature of this study and give written informed consent.

Exclusion Criteria:

1. Patients with medial group retropharyngeal node metastasis;
2. Aged > 65 or < 18;
3. Treatment with palliative intent;
4. Prior malignancy except adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer;
5. Pregnancy or lactation (consider pregnancy test in women of child-bearing age and emphasize effective contraception during the treatment period);
6. With history of previous RT (except for non-melanomatous skin cancers outside intended RT treatment volume);
7. Prior chemotherapy or surgery (except diagnostic) to primary tumor or nodes;
8. Any severe intercurrent disease, which may bring unacceptable risk or affect the compliance of the trial.