Salivary gland function and xerostomia in southern Chinese following radiotherapy for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is rare among Caucasians but very common among southern Chinese. No information is presently available on the relationship between salivary gland function and xerostomia in irradiated southern Chinese. Salivary gland function and xerostomia were measured in irradiated NPC patients, recently diagnosed NPC patients, and a matched control group. Stimulated whole saliva was collected from each participant and flow rate, pH and buffer capacity measured. All participants completed a multi-item dry mouth questionnaire. Comparisons were made using Chi-square and Mann-Whitney tests and correlations assessed using Spearman's rank correlation coefficients. The mean saliva flow rate and pH were significantly lower and the buffer capacity impaired in irradiated NPC patients compared with the other groups (P<0.01). Significantly more irradiated NPC patients had negative impacts associated with dry mouth generally, sticky saliva, and hoarse voice (P<0.01). Subjective dry mouth symptoms and associated reduced saliva flow were also relatively common in non-irradiated participants. Salivary gland hypofunction and xerostomia were major complications in irradiated NPC patients. In irradiated and non-irradiated southern Chinese, subjective dry mouth symptoms appeared to be correlated with actual salivary gland function.