The purposes of this study were to (a) explore the impact of xerostomia and saliva flow on quality of life and (b) validate the Taiwanese version of the Xerostomia Questionnaire (XQ) for patients undergoing radiotherapy (RT) for head and neck cancer in Taiwan. This was a prospective longitudinal study. Instruments consisted of the Xerostomia Questionnaire-Taiwan version (XQ-T) and the Medical Outcomes Study Short Form-36 Taiwan Version. Salivary output was measured by collecting unstimulated whole saliva. The questionnaires and measurements of salivary output were completed before RT was initiated and at two, four, six, and eight weeks after RT had started. Changes in xerostomia scores, quality of life, saliva flow, and predictors of quality of life over time were examined by using general estimating equations. The XQ-T is the first xerostomia measurement instrument developed for use with Taiwanese cancer patients and demonstrated excellent reliability and validity. Saliva flow was significantly correlated with XQ-T scores at two, four, six, and eight weeks after RT had started, but not before RT had begun. Saliva flow and quality-of-life scores significantly diminished and xerostomia scores significantly increased over the eight-week period. Saliva flow and XQ-T scores significantly predicted quality of life, after adjusting for the maturation effect. The results of this study show that the XQ-T is the first xerostomia measurement instrument to be developed for Taiwanese cancer patients and demonstrates excellent reliability and validity.
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