Non-invasive objective evaluation of radiotherapy-induced dry mouth.

Background: Dry mouth is a common complaint in patients undergoing radiotherapy. Here, we employed the oral moisture meter Mucus III to evaluate dry mouth in head and neck tumor patients before and after they underwent radiotherapy.

Methods: We recruited 17 newly diagnosed patients with pharyngeal squamous cell carcinoma or unknown primary squamous cell carcinoma, who received head and neck radiation therapy at Tokyo University Hospital in 2008-2010. The primary sites were the epipharynx (n = 1), oropharynx (n = 6), or hypopharynx (n = 5); it was unknown in five cases. Salivary function was assessed by a dry mouth questionnaire, resting saliva test, chewing gum test, and Mucus III, before (n = 17), immediately after radiotherapy (n = 10), and at 3 (n = 9) and 12 months after radiotherapy (n = 11).

Results: The questionnaire, resting saliva test, and chewing gum test at 3 and 12 months after radiotherapy indicated a significantly decreased resting and stimulated whole saliva flow rate than prior radiotherapy (P < 0.05 and P < 0.001). In contrast, Mucus III results showed significant worsening of xerostomia at 12 months after radiotherapy (P < 0.05).

Conclusion: Mucus III has been proven to be an objective diagnostic tool for patients with serious dry mouth, such as in patients with Sjogren's syndrome. However, we did not find a perfect correlation between Mucus III and other objective (resting saliva and chewing gum) and subjective (questionnaire) measures of dry mouth. To precisely diagnose radiotherapy-induced dry mouth, further improvement to the method is needed.