This is a prospective, non-randomized phase III study observing the cognitive function changes with conformal hippocampus avoidance during intensity modulated radiotherapy for T4 nasopharyngeal carcinoma patients.

All patients received intensity modulated radiotherapy or Tomotherapy with or without chemotherapy. Before radiotherapy, the patients will receive brain MRI scanning and the brain MRI images will be fused with the head and neck CT scan images. The investigators develop the treatment plan with hippocampus avoidance. Cognitive function are evaluated before,during and after radiotherapy. Dose-volume Histograms are got to analyze the associated factors.

Inclusion Criteria:

1. Histologically or cytologic confirmed nasopharyngeal carcinoma
2. ECOG performance scale 0-2
3. Tumor stage is T4N0-3M0-1 according to 8th American Joint Commission on Cancer edition
4. Adequate hepatic, renal and hematologic functions (hemoglobin ≥ 90g/L, platelets ≥ 100×10^9/L, neutrophils ≥ 1.5×10^9/L, serum transaminase < 2.5×the upper limit of normal(ULN), (If liver metastases, serum transaminase< 5×the ULN), creatinine clearance rate > 60ml/min.
5. Informed consent signed.

Exclusion Criteria:

1. History of malignant tumors.
2. Any severe complications contraindicated chemotherapy or radiotherapy.
3. Medical history of central nervous system, cognitive or psychological diseases;
4. Pregnant or nursing women.
5. Patients with mental disease cannot complete the questionaire.
6. MRI contraindication -

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