S583
Clinical – Head & neck
ESTRO 2026
(dysphagia and xerostomia) in oropharyngeal cancer (OPC) patients. Material/Methods: This prospective cohort included 617 consecutive patients with stage I–IV OPC treated with definitive (chemo)radiotherapy between 2007-2025 (NCT02435576). Radiotherapy techniques evolved from IMRT to VMAT (2014) and IMPT (using model- based patient selection, ~75% IMPT since 2018). Mean doses to the oral cavity, pharyngeal constrictor muscles (PCM), and contralateral parotid and submandibular glands were extracted; from 2018, both swallowing- and multi-organ-sparing VMAT and IMPT plans were optimized for all patients. Temporal trends in OOI doses, grade 2–4 dysphagia (CTCAE v4.0), and patient-rated moderate-to-severe xerostomia (EORTC QLQ-H&N35) at 6 months were analysed using moving averages (interval =100, partial), before and after the 2018 introduction of multi-organ sparing and IMPT. Partial moving averages smooth short-term fluctuations to highlight longer- term patterns, while allowing the inclusion of edge data where full intervals are not available. Results: OOI doses continuously declined over the 15-year period: oral cavity from 60Gy to 26Gy (Figure 1), PCM from 65Gy to 44Gy, contralateral parotid from 36Gy to 13Gy, and submandibular gland from 64Gy to 35Gy. The largest reductions occurred after the introduction of multi-organ sparing and proton therapy in 2018, exemplified by a decrease in oral cavity dose from 52Gy right before 2018 to 38Gy in 2019 and 26Gy in 2025. Dosimetric improvement over time relative to non-clinical backup plans was plotted (yellow, blue, green).Along with these dose reductions, dysphagia and xerostomia rates declined as well. Overall, the 6- month incidence of dysphagia decreased from 50% to 16%, and xerostomia from 58% to 39%. Implementation of VMAT with swallowing-sparing planning marked the first reduction in dysphagia, with continuous improvement after 2018 when multi-organ sparing and IMPT were introduced. Xerostomia rates remained stable until 2018 and also subsequently decreased.
Conclusion: Advances in radiotherapy and optimisation strategies have substantially reduced OOI doses and side effects in OPC patients. This, provides evidence of benefit even without the need for randomised controlled trials. Keywords: side effects, VMAT, multi-organ sparing Re - irradiation Using Modern IMRT/VMAT in Recurrent or Second Primary Head and Neck Squamous Cell Carcinoma: Clinical Outcomes and Toxicity Profile Digital Poster 2050 Reza Ghalehtaki 1,2 , Ava Yousefi 1 , Ehsan Saraee 1 , Romina Abyaneh 2 , Farshid Farhan 1 , Ali Kazemian 1 1 Radiation Oncology, Tehran University of Medical Sciences, Tehran, Iran, Islamic Republic of. 2 Radiation Oncology Research Center, Cancer Research Institute, Tehran, Iran, Islamic Republic of Purpose/Objective: To evaluate local control, survival, and treatment- related adverse events of re-irradiation, with or without systemic therapy, in patients with recurrent or second primary head and neck squamous cell carcinoma (HNSCC), using advanced radiotherapy techniques.
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