Qualitative and dosimetric assessment of radiation-induced xerostomia in patients with oral cancers treated with 3DCRT versus IMRT: A prospective observational study

Abstract

Background: Xerostomia is an important complication in patients with head-and-neck cancer treated with radiotherapy. It is caused by the radiation dose to the salivary glands situated in the lateral facial and submandibular regions, which are commonly included in or are close to the target volume.Objectives: Our primary objective was to evaluate xerostomia in patients treated with three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiation therapy (IMRT). We also aimed to identify the risk factors for the development of xerostomia and the treatment-related and dosimetric parameters associated with xerostomia in patients with oral cancers receiving radiotherapy.Materials and Methods: We enrolled 100 patients with oral cancers between Sept 2015 and Apr 2018 who were planned for adjuvant radiotherapy. Patients were treated with unilateral portals in 3DCRT or IMRT. Xerostomia was assessed using the Wake Forest National Cancer Institute Community Oncology Research Program Research Base (WF NCORP RB) # 97115 Questionnaire at baseline, treatment completion, and at 1, 4, and 7 months following the completion of radiotherapy. Detailed salivary gland dosimetric parameters including the minimum (Dmin), maximum (Dmax), and mean dose (Dmean) and other dose and volume parameters (e.g., D25, D50, D75, and V10–V60) were assessed through cumulative dose volume histograms (DVH). Multivariate analysis was performed to determine the factors associated with the development of xerostomia and assess the correlation with dosimetric parameters.Results: At a median follow-up of 20 (95% confidence interval [CI], 8–32) months, the V20, V25, V30, V40, V45, V50, V60, Dmin, and Dmean received by the ipsilateral parotid gland were significantly lower in patients treated with IMRT compared to those treated with 3DCRT (P < 0.001). After the completion of radiotherapy, the mean xerostomia scores at each follow-up were significantly lower in the patients who had received IMRT, compared to 3DCRT. At 7 months of completion of treatment, the mean score of xerostomia in the 3DCRT arm was 44.4, compared to 33.8 in the IMRT arm (P = 0.023). On multivariate analysis, Dmin, V30, V40, V45, V60, history of substance abuse, advanced age, and lower body weight were found to be associated with higher chances of xerostomia.Conclusion: Compared to 3DCRT, IMRT results in lower rates of xerostomia based on dosimetric as well as subjective analysis.