Radiation induced oral mucositis which may result in reduced quality of life is commonly seen during radiotherapy, especially combined with chemotherapy. This study is a prospective, single center, and exploratory study. Two contour methods of oral mucosal will be used in this study. All detail information will be recorded prospectively. The aim of this study is to explore predictive factors of acute radiotherapy induced oral mucositis in nasopharyngeal carcinoma patients treated with new precise radiotherapy (intensity modulated radiotherapy or tomography radiotherapy) by using different dosimetric parameters and clinically relevant variables.

To prospectively identify the predictive value of different dosimetric parameters and assess the predictors of acute radiation oral mucositis in nasopharyngeal carcinoma patients treated with intensity modulated radiotherapy or tomography radiotherapy.

Inclusion Criteria:

1.Clinical diagnosis of nasopharyngeal carcinoma. 2.7th version American Joint Committee on Cancer (AJCC) stage II-IVB. 3.Age must above 18. 4.Performance status must be 0 or 1 according to Eastern Cooperative Oncology Group.

5.Adequate bone marrow, renal, and hepatic function.

Exclusion Criteria:

1. Treatment with palliative intent.
2. Previous malignancy.
3. Pregnancy or lactation.
4. A history of previous radiotherapy, chemotherapy, or surgery (except diagnostic) to the primary tumor or nodes.
5. Any severe coexisting disease.

Between September 2016 and August 2018, consecutive patients with II-IVB nasopharyngeal carcinoma receiving intensity modulated radiotherapy or tomography radiotherapy.