ESTRO 2025 - Abstract Book

S980

Clinical – Head & neck

ESTRO 2025

demonstrating a small but not clinically significant benefit using the 5+5 method in the absence of mandated dysphagia optimisation.

Conclusion: The introduction of “5+5” contouring did not appear to lead to a detriment in efficacy outcomes. This research was supported by CRUK [C19677/A17226], CRUK/13/026 and conducted with support from AstraZeneca UK Limited

Keywords: oropharynx, 5+5, swallowing

References: 1. Mehanna, H., Gaunt, P., Kong, A. et al. CompARE: study protocol for a phase III randomised controlled platform trial comparing alternative regimens for escalating treatment of intermediate and high-risk oropharyngeal cancer. Trials 25, 50 (2024). https://doi.org/10.1186/s13063-023-07881-1 2. Grégoire V, Evans M, Le QT et al. Delineation of the primary tumour Clinical Target Volumes in laryngeal, hypopharyngeal, oropharyngeal and oral cavity squamous cell carcinoma: AIRO, CACA, DAHANCA, EORTC, GEORCC, GORTEC, HKNPCSG, HNCIG, IAG-KHT, LPRHHT, NCIC CTG, NCRI, NRG Oncology, PHNS, SBRT, SOMERA, SRO, SSHNO, TROG consensus guidelines. Radiother Oncol. 2018 Jan;126(1):3-24. doi: 10.1016/j.radonc.2017.10.016. Epub 2017 Nov 24. PMID: 29180076.

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Digital Poster Selection strategy for adaptive radiotherapy in patients with nasopharyngeal cancer: a single institution experience Elena Onorati 1 , Heleen Bollen 2,3 , Annouschka Laenen 4 , Anneleen Goedgebeur 3 , Sandra Nuyts 2,3 1 Department of Radiation Oncology, Campus Bio-Medico Univeristy of Rome, Rome, Italy. 2 Laboratory of Experimental Radiotherapy, Department of Oncology, University of Leuven, Leuven, Belgium. 3 Department of Radiation Oncology, Leuven Cancer Institute, University Hospitals Leuven, Leuven, Belgium. 4 Leuven Biostatistics and Statistical Bioinformatics Center, University of Leuven, Leuven, Belgium Purpose/Objective: Patients with nasopharyngeal cancer (NPC) experience significant anatomical changes during radiotherapy (RT). Since adaptive radiotherapy (ART) can be started either at a predetermined time during RT or in response to specific events, many questions arise regarding patient selection, timing and reliable triggers for re-planning. The study aimed to develop a method for the pre-treatment selection of NPC patients for ART and to identify the optimal timing for re-planning. Material/Methods: The population study included NPC patients treated at the University Hospital Leuven between 2016 and 2023. Volume changes during RT in the parotid glands, air cavities, maxillary sinuses and body contours at the nasopharyngeal and lower neck levels were evaluated retrospectively. Contouring was performed on simulation CT, weekly CBCTs and final day CBCTs, resulting in 8 measurements per parameter. At the nasopharyngeal level (odontoid process) and lower neck level (lower edge of C3), measurements included volume, transverse diameters, and radius angles of 50° and 310°. Kaplan-Meier analysis was used for overall survival (OS) and local control (LC), while longitudinal volumetric data were analysed using linear mixed models. Continuous variables were dichotomised to create a binary variable to define cut-off values for significant predictive variables. Results: Among the 47 NPC patients analysed, significant reductions in body contour and parotid glands volume were observed between week 3 and week 4 of treatment.