Secondary objectives are to assess the incidence of xerostomia subjectively by xerostomia specific &University of Washington Quality of Life Head and Neck Symptom questionnaire and objectively by sialometry and salivary scintigraphy after parotid-sparing IMRT+ SGT. We also intend to evaluate the speech and swallowing function of patients before and after radiation. All these functional outcomes will be correlated with the dose-volume histograms of salivary glands.