Prophylactic Radiotherapy Optimization for Enhanced Thyroid Function Protection in NPC

Inclusion Criteria:

1. Male or female, aged 18-70 years; 2. Pathologically confirmed nasopharyngealcarcinoma; 3. No positive lymph nodes in unilateral or bilateral regions III andIVa; 4. Clinical stage I-IVa (AJCC/UICC 8th edition), with no evidence of distantmetastasis; 5. Normal thyroid function; 6. ECOG performance status of 0-1; 7.Treatment-naïve patients who have not received any prior antitumor therapy; 6. Nocontraindications to radiotherapy or chemotherapy; 9. Adequate organ function,meeting the following criteria: Hematologic criteria: WBC ≥ 4.0 × 10⁹/L, ANC ≥ 1.5 × 10⁹/L, PLT ≥ 100 × 10⁹/L, HGB ≥ 90 g/L (no transfusion, blood products, orhematopoietic growth factors used within the past 7 days); Biochemical criteria: ALTand AST < 1.5 × ULN, ALP < 2.5 × ULN, total bilirubin < ULN, BUN and creatinine ≤ 1.5 × ULN or creatinine clearance rate ≥ 60 mL/min (calculated using theCockcroft-Gault formula).

2. Voluntarily agreed to participate in the study, signed the informed consent form,demonstrated good compliance, and agreed to follow-up.

Exclusion Criteria:

1. History of other malignant tumors (excluding basal cell carcinoma/squamous cellcarcinoma of the skin or cervical carcinoma in situ);

2. History of radiotherapy (excluding radiotherapy outside the planned target area forconditions such as melanoma);

3. History of neck surgery;

4. Any severe comorbidities that may pose risks to the study or affect compliance, suchas unstable heart disease requiring treatment, kidney disease, chronic hepatitis,poorly controlled diabetes (fasting blood glucose > 1.5 × ULN), or psychiatricdisorders;

5. History of hyperthyroidism, hypothyroidism, or immune-related thyroid disorders;

6. Other family or social factors, as judged by the investigator, may force the study'searly termination, compromise patient safety, or affect the collection of trialdata.