S1013
Clinical – Paediatric tumours
ESTRO 2026
the clivus, and the caudal limit of ethmoid sinus. Conclusion: This international consensus atlas establishes standardised guidelines for FS delineation in paediatric HNRT. It promotes contouring consistency, aiding dentofacial dose-effect research and future automated FS contouring tool development. References: 1. Mayo CS, Moran JM, Bosch W, Xiao Y, McNutt T, Popple R, et al. American Association of Physicists in Medicine Task Group 263: standardizing nomenclatures in radiation oncology. IJROBP 2018;100:1057–66 Keywords: late effects, facial deformation, atlas Digital Poster Highlight 2727 Real-world outcomes of patients with adult medulloblastoma: a retrospective, single-centre, 17-year experience. Kieran Palmer, Nicola O'Neill, Karthica Indramohan, Baker Kirresh, Sheetal Patel, Michael Kosmin, Naomi Fersht Neuro-oncology Team, Clinical Oncology Department, University College London Hospital, London, United Kingdom Purpose/Objective: Adult medulloblastomas are rare tumours with limited data to guide treatment, so management relies on paediatric experience. Dedicated adult studies are needed but currently limited by small patient numbers. Here, we present real-world outcomes from a large cohort managed at a tertiary neuro-oncology centre in London. Material/Methods: We performed a retrospective review of patients aged ≥ 16 years treated between July 2007 and December 2024. Where available, contemporary molecular classification helped to inform risk stratification. Recurrence-free survival (RFS) and overall survival (OS) were estimated using the Kaplan–Meier method from the date of surgery to the event of interest. Differences between survival curves were compared using the log-rank test. Results: 54 patients were included; median age (interquartile range) was 25 years (20–34) and 18 (33%) were female. 28 (52%) had classical medulloblastoma, 11 (20%) had desmoplastic, six (11%) had large cell morphology and nine (17%) were not classified. Molecular profiling was available for 49 (91%) patients and identified 19 (35%) as SHH-activated (12 TP53-wildtype and seven unknown TP53 status), five (9%) as WNT-activated and four (7%) with MYC and MYCN amplification. Most patients (50; 93%) had non-metastatic disease at
of feedback and refinementVirtual consensus meeting to finalise definitionsFinal review and approval of updated atlasA second paediatric HN case was used for validation. Ten ROs, uninvolved in development, delineated all FS using the atlas. Evaluation metrics included contouring time, confidence (5-point Likert scale), and qualitative feedback. Inter-observer variation against a gold standard (GS) determined by consensus between multi-disciplinary experts, was assessed using average surface distance. Results: DevelopmentSurvey responses were received from pROs representing 16 institutions from 13 countries. Consensus refinements added anatomical descriptors, the ethmoid sinus structure, clarified craniocaudal boundaries, and aligned nomenclature with Global Harmonization Group (AAPM TG263).1 A bone window was recommended for optimal visualisation. Atlas details are in Figure 1 and Table 1.
ValidationTen ROs (from 9 institutions, 9 countries) completed FS delineation; mean time was 2hrs 5min (range 45min – 2hrs 58min). Mean confidence was ≥ 3/5 for all structures. Agreement with GS volumes were highest for temporomandibular joint (L:0.33mm, R:0.51mm), nasal (0.41mm) and orbital (L/R:0.47mm), moderate for sphenoid (L:0.48mm, R:0.71mm), maxillary (L:0.73mm, R:0.78mm), and mandible (L:0.74mm, R:0.95mm) and lowest for ethmoid sinus (2.17mm).Qualitative feedback highlighted that the atlas was practical and user-friendly. Challenges included defining the mandible’s medial border (a large single bone anatomically), excluding teeth, vomer visualisation in paediatrics with incomplete ossification, lateral and cranial sphenoid limits near
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