Xerostomia-optimised IMRT Versus Standard IMRT in NPC

Inclusion Criteria: * Newly histologic diagnosis of nasopharyngeal non-keratinizing carcinoma (WHO II/III); * All genders, range from 18-70 years old; * ECOG score 0-1; * Clinical stage I-IVa (AJCC/UICC 8th); * Not received radiotherapy, chemotherapy and other anti-tumor treatment (including immunotherapy); * No contraindications to chemotherapy or radiotherapy; * Adequate organ function: white blood cell count ≥ 4×109/L, neutrophile granulocyte count ≥ 1.5×109/L, hemoglobin ≥ 90g/L, platelet count ≥ 100×109/L; alanine aminotransferase or aspartate aminotransferase \< 2.5×upper limit of normal; blood urea nitrogen or creatinine ≤ 1.5×upper limit of normal or endogenous creatinine clearance ≥ 60ml/min (Cockcroft-Gault formula); * Sign the consent form. Exclusion Criteria: * Level II involvement with extracapsular extension (ECE), and/or had a maximum nodal axial diameter (MAD) of greater than 3cm in level II ; -≥4 nodal regions of ipsilateral neck involvement; * Radiologically suspicious or confirmed involvement in level II area between skull base and the lateral process of C1; * Parotid lymph node and/or parotid gland involvement; * History of parotid disease or surgery; * Previous malignancy or other concomitant malignant disease; * Pregnancy or lactation.