ESTRO 2025 - Abstract Book

S2535

Physics - Autosegmentation

ESTRO 2025

3584

Digital Poster Dentofacial structures delineation in head and neck rhabdomyosarcoma patients Shermaine Pan 1 , Sarah Kelly 2,3,4 , Jasima Latif 1 , Lucy Siew Chen Davies 5,6 , Maria Chiara Lo Greco 2,3 , Coreen Corning 3 , Marianne Aznar 6 , Marinka Hol 7,8,9 , G.A. Amos Burke 10,11 , Julia Chisholm 12 , Henry Mandeville 13,14,2 1 Department of Proton Beam Therapy, The Christie NHS Foundation Trust, Manchester, United Kingdom. 2 QUARTET Project, European Society for Paediatric Oncology, Brussels, Belgium. 3 Medical Department (RTQA Unit), The European Organisation for Research and Treatment of Cancer (EORTC) Headquarters, Avenue E, Mourier 83, Brussels, Belgium. 4 Faculty of Medicine and Health Sciences, University of Ghent, Ghent, Belgium. 5 Department of Radiotherapy, The Christie NHS Foundation Trust, Manchester, United Kingdom. 6 Division of Cancer Sciences, University of Manchester, Manchester, United Kingdom. 7 Pediatric Oncology, Princess Maxima Center, Utrecht, Netherlands. 8 Department of Otorhinolaryngology, University of Utrecht, Utrecht, Netherlands. 9 Department of Maxillofacial Surgery, Amsterdam UMC, Duivendrecht, Netherlands. 10 Cancer Research UK Clinical Trials Unit (CRCTU), Institute of Cancer and Genomic Sciences/Sponsor representative, University of Birmingham, Birmingham, United Kingdom. 11 Paediatric Oncology, Birmingham Women's and Children's NHS Foundation Trust, Birmingham, United Kingdom. 12 Children and Young People's Unit, The Royal Marsden Hospital and the Institute of Cancer Research, Sutton, United Kingdom. 13 Department of Radiotherapy, The Royal Marsden Hospital and the Institute of Cancer Research, Sutton, United Kingdom. 14 Department of Proton Beam Therapy, University College London Hospitals, London, United Kingdom Purpose/Objective: Dentofacial deformation is a late sequela in children treated with radiotherapy for head and neck rhabdomyosarcoma (HNRMS). A published international survey [1] showed delineation of dentofacial structures (DFS) is time-consuming and has a lack of standardisation, hence often not delineated. We present a review on DFS contours submitted to QUARTET, a SIOP Europe platform for centralised peer review [2,3], as part of a HNRMS international trial (FaR-RMS, NCT04625907) [4] Material/Methods: DFS contours for all HNRMS cases submitted to QUARTET were reviewed on Velocity (version 4.1, Varian Medical Systems). Facial bones contours (facial bones composite, ethmoid, mandible, temporomandibular joint (TMJ), maxilla, sphenoid, orbits, nasal bone, and teeth) were compared with a consensus-based anatomical atlas. Major difference was defined as one or more missing DFS and/or three or more partially completed structures, and minor differences as incomplete contours of two or less DFS. Individual DFS were additionally evaluated to determine whether left and right structures were delineated separately. Results: A total of 125 cases of HNRMS from 11 countries were reviewed, 8 excluded as data on DFS delineation were not available. Median age was 9 (range 1 – 45). The main four subsites of tumours include orbit (27/117), paranasal sinus (18/117), nasopharynx (19 /117), masticatory space (18 /117). Other subsites (35/117) include parapharyngeal space, parotid, oropharynx, nose, maxilla among other subsites. Majority of patients (70 %) received proton beam therapy. Of the 117 cases, 12 cases had no DFS delineation. Thirty two of 105 (30%) cases had only mandible delineated, which often included TMJ as one combined structure; only 4 separated the left and right mandible contour. Twenty one (20%) patients had a composite facial bones contour, some also included non-DFS structures. Only 15 patients (14%) had minor differences. Most (90/105, 86%) patients had major differences, as only one or some DFS were delineated.