The goal of this clinical trial is to learn about the effect of nutritional management on radiation-induced oral mucositis in patients with advanced head and neck cancer during the peri-radiotherapy period . The main questions it aims to answer are:

• [question 1]Whether whole-course nutritional intervention can improve radiation-induced oral mucositis in patients with HNC.
• [question 2]Whether whole-course nutritional intervention can improve nutritional status and inflammation.

Participants will be treated according to the NCCN guidelines. In addition, clinical pharmacists and registered dietitians provided nutritional intervention strategies based on clinical and nutritional assessments for the patients in the peri-radiotherapy nutrition group.

Researchers will compare clinical routine examination and nutritional indicators between the standard treatment group and the peri-radiotherapy nutrition management group to see if nutrition management effects.

Inclusion Criteria:

• Aged between 18 and 80 years old
• Advanced head and neck cancer (III-IV inoperable) is clearly diagnosed
• Predicted survival time > 3 months
• Radical radiotherapy combined with chemotherapy or immunotherapy was performed in our hospital
• The patient has clear consciousness and no communication disorder
• Informed consent and voluntary participation in this study

Exclusion Criteria:

• Patients with previous surgery or radiotherapy for head and neck cancer
• Patients with concurrent or previous history of other tumors
• Distant metastasis
• Patients with allergy, intolerance or contraindication to enteral nutrition or parenteral nutrition
• Severe renal insufficiency (eGFR<30ml/min/1.73m2)
• Combined with poorly controlled metabolic diseases such as diabetes
• Doctors or researchers deem that they are not suitable to participate in the study.