Sparing submandibular gland to alleviating acute xerostomia in patients with nasopharyngeal carcinoma treated with helical tomotherapy: Evaluation by diffusion kurtosis imaging

Purpose To identify the clinical significance of sparing submandibular glands (SMG) for the amelioration of acute xerostomia using diffusion kurtosis imaging (DKI) in nasopharyngeal carcinoma (NPC) patients treated with helical tomotherapy (HT). Materials and methods The prospective study enrolled 42 participants treated with HT. All patients underwent five times of DKI scans before HT (pre-HT), in the middle of the HT course (mid-HT), immediately after HT (post-HT), and 1 months (1m-HT), 3 months post-HT(3m-HT). Mean diffusion (MD) and mean kurtosis (MK) of SMG, parotid glands (PG) and sublingual glands (SLG), saliva flow rate measures under resting (uSFR) and stimulated condition (sSFR), and xerostomia questionnaire scores (XQ) were recorded. Comparisons between the SMG-spared and -unspared groups were analyzed using two-factor repeated-measures ANOVA for the group as the inter-subject factor and the time as the intra-subject factor. Results When sparing SMG, the dose of spared-SMG and ipsilateral SLG was lower compared to that of unspared glands (p < 0.001). MD of spared-SMG and ipsilateral SLG in SMG-spared group were lower than that of SMG-unspared group (the simple effect for the group, p-value at mid-HT, post-HT, 1m- and 3m-HT was 0.014, 0.011, 0.000 and 0.000, respectively), MK of spared-SMG was higher conversely (the main effect for the group, p < 0.001), while uSFR and sSFR were significantly lower in SMG-unspared group (the main effect for the group, p = 0.002, and p = 0.045, respectively). No significant differences were detected in MK of SLG, MD/MK of PG, and XQ between the two groups (the main effect for the group, p values were 0.9, 0.37, 0.15, 0.86, respectively). There were significant differences in the effect of the time for all MD/MK of the salivary glands and for uSFR, sSFR, and XQ between the SMG-spared and -unspared groups (p values were all <0.001). Conclusion Sparing SMG is of great clinical significance in alleviating acute xerostomia for NPC patients treated by helical tomotherapy as evaluated by diffusion kurtosis imaging and saliva flow rate.