Inclusion Criteria:1) newly diagnosed, histologically confirmed World Health Organization (WHO) type II-III NPC; 2) stage I-IVa (T1-4 N0-3M0) according to the staging system of the 8th American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC); 3) no prior antitumor therapy; 4) no tumor involvement in salivary gland; 5) no parotid glands disorder and no history of parotid glands surgery; 6) ages between 18 and 70 years; 7) Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1, and 8) adequate organ function Exclusion Criteria: 1) used salivary stimulating or protecting agent; 2) metachronous or synchronous malignancy; 3) pregnancy or lactation; or 4) severe comorbidities. The pretreatment evaluation included a complete history and physical examination, nasopharyngoscopy, chest X-ray, complete blood count, liver and renal biochemistry, and magnetic resonance imaging (MRI) of the head and neck.