The influence of radiation technique on xerostomia in head and neck cancer patients - Prospective study

Abstract

Background: Irradiation of salivary glands during the treatment of head and neck cancer may lead to an alteration in the amount of saliva produced. Because of this, patients can suffer dryness of the mouth with oral discomfort, taste disturbance and dental decay. Aim: The aim of this study is to estimate late toxicity dependence on radiotherapy method. The main goal is to investigate the correlations between the radiation doses in salivary glands and their salivary excretion fractions (SEF) measured by dynamic scintigraphy. Materials/Methods: In 40 patients with pharyngeal and laryngeal cancer irradiated by IMRT or conformal 3D to a total dose of 62.5-72.0Gy, parotid SEFs were measured. Parotid dose-volume histograms were obtained from 3D computer treatment planning. SEF measurements were performed before (baseline), and 6 weeks and 6 months after radiotherapy by 185MBq 99 Tc injected intravenously and next SEF rates were analysed in relation to radiation doses accumulated. The late radiation toxicity of salivary glands was tested according to the CTC v. 3.0 and SOMA-LENT scales. The non-parametric Mann Whitney test was used for the estimation of relationships. Results: Pre- and post-treatment SEFs were measured in 31 patients treated by IMRT and in 9 patients treated by 3D CRT. Six weeks after radiotherapy SEF was generally lower by 34%, and 6 months after irradiation by 29.3% in IMRT technique. In 3D CRT relatively it was lower: after 6 weeks by average 52% and after 6 months by 35.5%. Late radiation toxicity of salivary glands was observed at a similar level according to CTC and SOMA-LENT scales in both methods of radiotherapy. Conclusions: The level of SEF in parotid glands measured 6 weeks after radiotherapy clearly reflects the dose-response relationship of irradiated salivary tissue; 6 months later changes of SEF are the result of partial recovery of parotids. The results of sparing salivary glands can be optimized in the future; that is, a further reduction of xerostomia can be achieved by using improved IMRT techniques and focusing on sparing major and minor salivary glands.