Could less radiation be just as effective for neck cancer?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Age 18-70 years. 2. Pathologically confirmed WHO type I, II, or III nasopharyngeal carcinoma. 3. Staged as T1-4N0-3 M0, Stage I-III according to the UICC/AJCC 9th edition staging system. 4. Absence of distant metastasis confirmed by systemic FDG PET/CT (or whole-body bone scan plus chest CT and abdominal ultrasound). 5. Ability to undergo MRI examination. 6. Adequate major organ function meeting radiotherapy requirements: 1. Hematopoietic function: Hemoglobin ≥9 g/L, Platelets ≥100×10⁹/L, WBC ≥3.5×10⁹/L, Neutrophils ≥2.0×10⁹/L. 2. Liver function: ALT and AST \< 2.5 × ULN, Bilirubin \< 1.5 × ULN. 3. Renal function: Creatinine clearance ≥50 mL/min or serum creatinine within normal range. 4. Patients with clinical symptoms will be evaluated based on specific manifestations. 7. ECOG performance status 0-1; absence of severe comorbidities (e.g., severe pulmonary hypertension, cardiovascular disease, peripheral vascular disease, severe chronic heart disease) that may preclude radiotherapy. Cardiac function class 1-2 (NYHA classification). 8. Life expectancy ≥12 months. 9. Patients must be informed of the study details and provide written informed consent. Exclusion Criteria: 1. Pathology not confirming WHO type I, II, or III nasopharyngeal carcinoma. 2. Distant metastasis identified clinically or radiologically before treatment, or presence of skip metastases in cervical lymph nodes. 3. Pregnancy (confirmed by serum or urine β-HCG test) or lactation. 4. Unwillingness to provide informed consent. 5. Prior radiotherapy to the head and neck region. 6. Comorbidities or other factors that may contraindicate photon or carbon-ion therapy. 7. Inability to comply with regular follow-up due to psychological, social, familial, or geographical reasons. 8. Known allergy to chemotherapeutic agents (e.g., cisplatin, docetaxel, gemcitabine) or contrast media used in the study's imaging examinations. 9. Contraindication to contrast-enhanced MRI. 10. Major organ dysfunction, or severe uncontrolled concurrent infection or medical illness (e.g., decompensated cardiac, pulmonary, renal, or hepatic failure). 11. History of immunodeficiency (positive HIV test), other acquired/congenital immunodeficiency disorders, or history of organ/allogeneic bone marrow transplantation. 12. History of other malignancies prior to enrollment (except for basal cell carcinoma of the skin). 13. History of substance or alcohol abuse. 14. Any other condition deemed by the investigator to potentially lead to study discontinuation, including co-morbidities (including psychiatric) requiring concomitant treatment, severely abnormal laboratory values, or familial/social factors compromising patient safety or data integrity.