More than 70% of head and neck malignant tumors require radiotherapy intervention during their treatment, but dry mouth and oral disorders caused by impaired parotid function due to radiotherapy have been the most common complications of radiotherapy for head and neck malignant tumors, which seriously affect the quality of patients’ survival. The anatomical structure of head and neck is complex, including many important organs and tissues such as eye, crystal, optic nerve, optic cross, pituitary gland, brain stem, spinal cord and parotid gland. The parotid gland secretes about 60% to 65% of oral saliva, which is very sensitive to X-rays. When the irradiation dose is 10~15Gy, the saliva secretion will be significantly reduced; when the irradiation dose is higher than 40~50Gy, it can cause permanent functional damage to the parotid gland, resulting in serious oral disorders such as dry mouth and oral mucosal ulcers. Since the target area of head and neck tumor is intricately interwoven with the organs and tissues around it, traditional two-dimensional radiotherapy and three-dimensional conformal radiotherapy basically cannot achieve the purpose of preserving the function of parotid gland. Intensity-modulated radiotherapy, also known as conformal intensity-modulated radiotherapy, was first proposed by American scholars in the 1970s and is considered to be one of the most important changes in the history of radiation oncology. It is considered to be a change in the history of radiation oncology and will be the mainstream of radiation therapy technology in this century. The so-called conformal intensity modulated radiation therapy refers to a radiation therapy technique that uses various physical means to adjust and control the intensity distribution of X-rays in the irradiation field according to the shape of the tumor target area to produce different dose gradients, so as to increase the lethal high dose irradiation to the tumor target area, while controlling the normal tissues around the tumor below the tolerated dose. Firstly, it is to achieve three-dimensional conformal irradiation to the tumor target area; secondly, it is to make the tumor target area and the adjacent sensitive organs to obtain the regulation of irradiation dose intensity. The goal is to maximize the gain ratio of radiotherapy, i.e. to maximize the radiation dose to the tumor lesion, while making the surrounding normal tissues and organs less damaged by the radiation treatment. Intensity-modulated radiation therapy for head and neck malignancies can increase the dose to the target area while reducing the dose to the surrounding vital organs, especially to preserve most of the parotid function. Clinical studies have shown that when the average dose to the parotid gland is less than 26Gy, it is expected to preserve most of the function of the parotid gland. Therefore, intensity-modulated radiotherapy for head and neck malignancies is also called “cheek-conserving radiotherapy”. Reducing the dose to the parotid gland and preserving the function of the parotid gland is one of the most important objectives. It has been confirmed that nasopharyngeal carcinoma is the most suitable malignant tumor for intensity-modulated radiation therapy among head and neck tumors. Nasopharyngeal carcinoma is also a tumor that can be cured by radiotherapy, and its 5-year survival rate can reach over 70%. Precautions for radiotherapy of head and neck malignant tumors Precautions before radiotherapy 1. Clear diagnosis, including pathology, CT, MRI, and even PET/CT imaging. Oral treatment: dental cleaning, treatment of affected teeth, dental caries, root remnants, removal of metal crowns, and waiting for the wound of extracted teeth to heal before starting radiotherapy. 3.Quit smoking and alcohol. 4.Do not eat smoked and pickled food. 5. Ask women of childbearing age about their menstrual history, and if the pregnancy is combined, it should be terminated before radiotherapy. 6, good personal hygiene, cut short hair. Precautions in radiotherapy 1.Give high protein and high vitamin diet. 2. Pay attention to oral hygiene. Brush teeth with fluoride toothpaste. If the oral mucosa reaction is severe and affects eating, infusion and related symptomatic treatment can be given. 3. Protect the skin in the radiation field from chemical stimulation, protect it from the sun, keep it dry, and do not touch water as much as possible, and apply special radiation protection cream after radiotherapy (prohibited 6 hours before radiotherapy). Post-radiation therapy precautions 1.Regular review The review time can be based on medical advice, in principle, it is recommended to review once every 1-2 months in the first 1-2 years, and once or twice a year after the third year. 2.Prevent colds and head and neck infections to avoid acute cellulitis in the neck, and go to the hospital for symptomatic treatment if there is local redness and swelling. 3.Pay attention to oral hygiene Do not extract teeth within 2~3 years after radiotherapy, and inform the dentist of the history of facial and neck radiotherapy when it is necessary. 4.Protect the skin of the radiation field from physical and chemical stimulation, protect it from the sun and keep it dry. 5.Married women should consider childbirth after 3 years. 6.Enhance nutrition, regular life and happy spirit. It is normal to have radioactive edema in the radiotherapy area 2~6 months after radiotherapy, but if you have difficulty in breathing, you should go to the emergency room of the nearby hospital and ask the emergency doctor for urgent treatment.