To Evaluate the Efficacy and Feasibility of Modified Reduce-volume Target IMRT in the Treatment of Patients With Non-metastatic NPC

Inclusion Criteria: 1. Pathologic diagnosis (pathologically confirmed by nasopharyngeal biopsy) was nasopharyngeal carcinoma; 2. Newly diagnosed, non-metastatic and treated with modified reduce-volume IMRT; 3. Patients with baseline MRI date of nasopharynx and neck, and completed the first course of treatment in our hospital; 4. Diagnosis time: November 1, 2014 to December 31 , 2017 Exclusion Criteria: 1. Disease progression during IMRT; 2. Previous malignancy or other concomitant malignant diseases; 3. The evaluation information of tumor efficacy can not be obtained; 4. Receive blind treatment in other clinical research.