ESTRO 2025 - Abstract Book

S1074

Clinical – Head & neck

ESTRO 2025

Purpose/Objective: The parotid glands account for approximately 65% of stimulated salivary flow, with peak activity during eating. In comparison, the submandibular glands are responsible for about 90% of unstimulated salivary flow, particularly during rest and sleep. Although sparing the parotid glands has significantly reduced radiation-induced xerostomia, the subjective improvement in patient-reported dryness has been inconsistent. Nutting et al. reported a less than 10-point improvement on a 0–100 Xerostomia Questionnaire scale, deemed clinically insignificant. 1 Hence, we conducted an assessor-blinded randomized controlled trial comparing submandibular and parotid gland sparing versus parotid sparing alone using volumetric modulated arc therapy in head and neck cancer patients, incorporating both objective and subjective evaluations. We evaluated submandibular sparing using the Xerostomia Questionnaire, RTOG toxicity criteria, sialometry, and salivary scintigraphy. Material/Methods: We conducted an assessor-blinded superiority-design randomized controlled trial at a tertiary cancer center. Adults (>18 years) with histologically confirmed head and neck squamous cell carcinoma, no distant metastases, ECOG PS 0–2, and planned for radical radiotherapy with or without chemotherapy using volumetric modulated arc therapy were included. Exclusion criteria were prior head and neck radiotherapy, bilateral submandibular gland tumour involvement, and pre-existing salivary gland disease. Parotid and submandibular glands were contoured per Water et al. and Brouwer et al. guidelines. 2 Xerostomia was evaluated using the University of Michigan Xerostomia Questionnaire, face-validated by two physicians with higher scores reflecting more severe xerostomia. 3 A dose of 66-70.4 Gy in 30-32 fractions was delivered to the high-risk PTV, while the low-risk PTV (elective nodal areas) received 54 Gy in 30 fractions. Results: We were unable to spare the submandibular glands in all patients in the submandibular sparing arm, so a per protocol analysis was performed. A statistically significant difference in XQ scores was observed at 6 months, favoring submandibular sparing (39 ± 27.15 vs. 59.73 ± 17.61, p=0.04). The unstimulated salivary flow rate at 3rd month was 0.30ml/min +/- 0.13 vs 0.30ml/min +/- 0.14, p=1.00 and at 6th month was 0.36ml/min +/- 0.16 vs 0.30ml/min +/- 0.10 p=0.35 in the spared and unspared arms respectively. Conclusion: Our study showed significant improvement in xerostomia by sparing the submandibular glands, with better XQ scores, and increased salivary flow rates in the spared arm. There were no marginal failures near the spared glands. 4 Sparing of both the ipsilateral and contralateral submandibular glands is feasible and should be the standard of care. References: 1. Nutting CM, et al.Parotid-sparing intensity modulated versus conventional radiotherapy in head and neck cancer (PARSPORT): a phase 3 multicentre randomised controlled trial. Lancet Oncol. 2011 Feb;12(2):127–36. 2. van de Water TA, et al . Delineation guidelines for organs at risk involved in radiation-induced salivary dysfunction and xerostomia. Radiother Oncol. 2009 Dec;93(3):545–52. 3. Eisbruch A, Kim HM, et al. Xerostomia and its predictors following parotid-sparing irradiation of head-and-neck cancer.Int J Radiat Oncol Biol Phys. 2001 J 4. Mf G, et al. Submandibular-gland-sparing radiation therapy for oropharyngeal squamous cell carcinoma: patterns of failure and xerostomia outcomes. Radiat Oncol Lond Engl. 2014 Nov 26 Keywords: submandibular sparing xerostomia