257 - Comparison of Xerostomia in Head and Neck Cancer Patients Undergoing Radiation with and without Parotid Duct Sparing via MRI Sialography: A Randomized Control Study

Purpose/Objective(s): Despite parotid gland–sparing radiotherapy, xerostomia remains a major dose-limiting toxicity in head and neck cancer (HNC). Emerging evidence suggests that radiation dose to the parotid duct may better predict salivary dysfunction than mean gland dose. We hypothesized that MRI sialography–guided duct sparing would reduce patient-reported xerostomia compared with conventional parotid gland sparing

Materials/Methods: In this single-institution prospective randomized controlled trial at a tertiary cancer center in eastern India, 30 patients with non-metastatic HNC were randomized 1:1 to (1) MRI-guided parotid duct–sparing radiotherapy (interventional arm) or (2) conventional parotid gland–sparing radiotherapy. MRI sialography (3T, 1.2 cm slices) was co-registered with planning CT to visualize and contour the duct. Planning required =95% of the Planning Target Volume (PTV) to receive =95% of the prescribed dose. Dose constraints were =26 Gy for the parotid gland and =14 Gy for the parotid duct. All patients received volumetric modulated arc therapy (VMAT). The primary endpoint was patient-reported xerostomia at 3 months using PRO-CTCAE and EORTC QLQ-H&N35. Patients were assessed weekly during treatment and at 1, 3, and 6 months post-radiotherapy. Categorical outcomes were compared using Fisher’s exact test (p<0.05).

Results: PTV coverage and parotid gland constraints were achieved in all plans. Mean parotid duct doses were 11.30 Gy (right) and 11.06 Gy (left). At 3 months, severe xerostomia (PRO-CTCAE) occurred in 67% (10/15) of the conventional arm versus 0% (0/15) of the interventional arm (absolute risk reduction 67%, p<0.001). On QLQ-H&N35, 60% (9/15) versus 0% reported “very much” dry mouth (p<0.001). At 6 months, xerostomia improved in both arms without significant differences, though milder symptoms persisted with duct sparing; limited evaluable numbers reduced statistical power.

Conclusion: MRI sialography–guided parotid duct sparing significantly reduces early radiation-induced xerostomia (ARR 67%) .This biologically informed strategy may refine organ-at-risk contouring and improve early quality of life, warranting validation in larger cohorts. Patient reported Xerostomia at 3 months