Predictors for improvement of xerostomia in nasopharyngeal carcinoma patients receiving intensity-modulated radiotherapy

To identify predictors for improvement of xerostomia in patients with nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT). Patients diagnosed with stage I-IVb NPC (according to the 7th edition of the American Joint Committee on Cancer) between September 2015 and March 2016 were retrospectively analyzed. All the patients received IMRT. Predictors for improvement of xerostomia were analyzed using logistic regression analysis. Receiver operating characteristic curve analysis was used to identify the most appropriate cut-off values for predicting factors. This study included 195 patients: xerostomia improved in 109 patients and xerostomia remained unchanged in 86 patients. Volume of the parotid gland <= 52.2 cm(3) was a risk factor for xerostomia improvement (odds ratio [OR]=3.506, 95% confidence interval [CI]: 1.932-6.362, P=.001). The mean dose of <39 Gy to the ipsilateral parotid gland was a protective factor (OR=0.417, 95% CI: 0.271-0.641, P=.001). V30 of the contralateral parotid gland <= 52% was a protective factor (OR=0.593, 95% CI: 0.462-0.760, P=.001). Volume of the parotid gland, the mean dose of the ipsilateral parotid gland, and V30 of the contralateral parotid gland were independent predictors for improvement of xerostomia.