S1012
Clinical – Paediatric tumours
ESTRO 2026
7 Department of Oncology, University College London Hospitals, London, United Kingdom. 8 Department of Oncology, Great Ormond Street Hospital for Children, London, United Kingdom. 9 Department of Radio- oncology and Radiotherapy, Staedtisches Klinikum Karlsruhe, Karlsruhe, Germany. 10 Department of Radiation Oncology, University of Florida, Florida, USA. 11 Department of Radiation Oncology, institut Curie, PSL Research University, Paris, France. 12 Department of Radiation Oncology, St. Jude Children’s Research Hospital, Memphis, USA. 13 Department of Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands. 14 Department of Oncology, Oslo University Hospital, Oslo, Norway. 15 Department of Radiotherapy, The Royal Marsden, London, United Kingdom. 16 Radiotherapy Department, MSC National Research Institute of Oncology Gliwice Branch, Gliwice, Poland. 17 Radiotherapy Clinic, MSC National Research Institute of Oncology Krakow Branch, Krakow, Poland. 18 Department of Oncology, Mälar Hospital, Eskilstuna, Sweden. 19 Department of Radiation Oncology, Acibadem MAA University, Istanbul, Turkey. 20 Radiation Oncology, Hospital Universitario de Badajoz, Badajoz, Spain. 21 Proton Therapy Department, Trento Hospital Azienda Provinciale per i Servizi Sanitari (APSS), Trento, Italy. 22 Department of Radiotherapy and Radiation Oncology, Technische Universität Dresden, Dresden, Germany. 23 Paediatric and Late Effects & Lung Units, Peter MacCallum Cancer Centre, Melbourne, Australia. 24 Prinses Maxima Center for Pediatric Oncology, Prinses Maxima Center for Pediatric Oncology, Utrecht, Netherlands. 25 Department of Clinical Oncology, The Christie NHS Foundation Trust, Manchester, United Kingdom Purpose/Objective: Radiation therapy (RT) for head and neck (HN) cancer in children can cause life-altering dentofacial side effects e.g., facial deformation. Consistent delineation of facial structures (FS) is essential for dose evaluation and understanding treatment impact; however, no standardised paediatric guidance exists. We developed and validated an international consensus atlas to standardise FS delineation. Material/Methods: The atlas provides detailed contouring guidance for key FS, initially drafted by a paediatric specialist radiologist, radiation oncologist, and research radiographer on a paediatric HN case contoured in Eclipse (Varian, v18.0) and uploaded to an in-house developed web-based platform. All structures except vomer and nasal included separate left/right (L/R) segmentations.Expert paediatric radiation oncologists (pROs), identified via an international dentofacial RT survey, contributed to atlas development following a multi-step consensus process:Online survey review of proposed FS and anatomical boundariesIncorporation
(median DSC 0.90 and maximum ASD 4.32). To improve consistency, it was agreed that non-infiltrated surfaces in contact with the tumour before surgery should be included in the GTVp_pre. Standard margins should be applied to create the CTVp_pre_4500, which should then be edited to avoid (if not infiltrated) the skin, lungs, and heart and to include the surgical bed.
Conclusion: Delineation workshops highlighted significant variations in target delineation for ES. The consensus obtained will be used to implement existing guidelines and support clinicians. Keywords: Ewing Sarcoma
Proffered Paper 2712 Facial Structure Delineation in Paediatric Radiation Therapy: International Consensus Atlas to Support Dentofacial Side Effect Mitigation Lucy SC Davies 1,2 , Vivian Tang 3 , Thankamma V Ajithkumar 4 , Dario Di Perri 5 , Claudio Fuentes 6 , Mark N Gaze 7,8 , Beatrix Hueltenschmidt 9 , Daniel J Indelicato 10 , Emmanuel Jouglar 11 , Matthew Krasin 12 , John H Maduro 13 , Henriette Magelssen 14 , Henry Mandeville 15,7 , Aleksandra Napieralska 16,17 , Zahra Taheri-Kadkhoda 18 , Enis Özyar 19 , Joaquín J Cabrera Rodríguez 20 , Barbara Rombi 21 , Chiara Valentini 22 , Greg Wheeler 23 , Marcel van Herk 2 , Marinka Hol 24 , Marianne Aznar 2 , Cynthia L Eccles 1,2 , Shermaine Pan 25 1 Department of Radiotherapy, The Christie NHS Foundation Trust, Manchester, United Kingdom. 2 Division of Cancer Sciences, The University of Manchester, Manchester, United Kingdom. 3 Department of Radiology, Manchester University NHS Foundation Trust, Manchester, United Kingdom. 4 Department of Oncology, Cambridge University Hospitals NHS Trust, Cambridge, United Kingdom. 5 Department of Radiation Oncology, Cliniques Universitaires Saint-Luc, Brussels, Belgium. 6 Department of Radiation Oncology, University Hospital NS Candelaria, Santa Cruz de Tenerife, Spain.
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