A longitudinal study on radiation induced xerostomia in radiotherapy of nasopharyngeal carcinoma patients

Abstract

Background: Xerostomia is the most common post-radiotherapy (post-RT) complication in nasopharyngeal carcinoma (NPC) patients. This longitudinal study evaluated the impact of radiotherapy on saliva flow rate of major salivary glands and patients’ quality of life due to xerostomia. Methods: 27 NPC patients treated by intensity modulated radiotherapy in 2018 were recruited. Resting saliva flow rates of individual saliva gland including parotid and submandibular glands were measured before radiotherapy, at 6-month, 12-month and 18-month post-radiotherapy (postRT). At the same time points, patients’ feedback on the severity of xerostomia was obtained from a validated questionnaire. Trend lines of the saliva flow rate and questionnaire scores were plotted, and the correlations of salivary gland doses and the percentage change of saliva flow rate at the time of greatest impact were also investigated. Results: Similar doses were received by the parotid gland and submandibular gland. The saliva flow rates of the parotid gland and submandibular gland showed significant decrease of over 80% at 6 months post-RT and stayed at similar low level thereafter. There was no significant correlation between post-RT saliva flow rate changes and mean doses received by the glands. For the xerostomia questionnaire scores, the feelings of dryness and comfortability of mouth deteriorated significantly at 6 months post-RT. Great impacts of xerostomia on sleeping, speaking, eating and wearing dentures were also observed at 6 months post-RT and they remained fairly constant afterward. Conclusion: The average mean doses to parotid and submandibular glands were around 35 Gy in IMRT of NPC patients, which significantly reduced the saliva flow rates of the parotid and submandibular glands. The impact was greatest at 6 months post-RT and was long lasting. Patients’ quality of life was affected by the severity of xerostomia and the effects showed similar pattern as the saliva flow rates.