The Protection of Thyroid Function in IMRT for Nasopharyngeal Carcinoma

Inclusion Criteria:

1. The pathological diagnosis was newly diagnosed non-keratinizing squamous cell carcinoma nasopharyngeal carcinoma.
2. The clinical stage is T1-4N0-3M0 (stage I\~IVa, UICC/AJCC 8th edition);
3. There is no history of hypothyroidism or hyperthyroidism before treatment;
4. Using intensity-modulated radiotherapy technology,
5. Complete radical dose radiotherapy;
6. KPS≥70 points;
7. Age 18-70 years old;
8. Male or female who is not pregnant or lactating;
9. Hematological examination: white blood cells \> 4×109/L, neutrophils \> 2×109/L, hemoglobin \> 90g/L, platelets \> 100×109/L;
10. Liver function: ALT, AST \< 1.5×ULN, ALP \< 2.5×ULN, bilirubin \< ULN.
11. Renal function: creatinine \> 60 ml/min;
12. The patient signs the informed consent form;

Exclusion Criteria:

1. WHO pathological classification is keratinizing squamous cell carcinoma or basaloid carcinoma;
2. palliative treatment;
3. Have a history of other malignant tumors;
4. Pregnant or lactating women (women of childbearing age should consider taking a pregnancy test, and patients are required to use effective contraception during treatment);
5. Have a history of neck surgery;
6. Have a history of hyperthyroidism or hypothyroidism.
7. Previous history of head and neck radiation therapy;