Reduced-dose Versus Standard Dose Radiotherapy for Nasopharyngeal Carcinomain

Inclusion Criteria: 1. Patients newly diagnosed with histologically confirmed non-keratinizing NPC (WHO type II or III). 2. Stage II-III（8thAJCC/UICC staging system) 3. Aged 18-70 years 4. ECOG = 0-1 5. HGB≥90 g/L，WBC≥4×109 /L，PLT≥100×109 /L 6. ALT,AST\<1.5 x ULN；TBIL\<1.5×ULN 7. CCR≥60ml/min or Cr\<1.5×ULN 8. CR/PR and EBVDNA undetectable after induction chemotherapy 9. Signed informed consent Exclusion Criteria: 1. WHO Type keratinizing squamous cell carcinoma or basaloid squamous cell carcinoma 2. Age \<18 or \>70years 3. Treatment with palliative intent 4. Prior malignancy except adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer 5. Pregnancy or lactation 6. History of previous radiotherapy (except for non-melanomatous skin cancers outside intended RT treatment volume) 7. Prior chemotherapy or surgery (except diagnostic) to primary tumor or nodes 8. Any severe intercurrent disease, which may bring unacceptable risk or affect the compliance of the trial, for example, unstable cardiac disease requiring treatment, renal disease, chronic hepatitis, diabetes with poor control (fasting plasma glucose \>1.5×ULN), and emotional disturbance