S1001
Clinical – Paediatric tumours
ESTRO 2026
schemes before and after 2013.In the subset of PF patients (95.29%), 1q gain (1q+) independently predicted poor RFS and OS in multivariate analysis (p=0.03 and p=0.046, respectively). Conclusion: A lower RFS was linked to grade 3 and a low RT dose. Poor OS was associated to grade 3, younger age at RT, lateralized tumors, incomplete surgery, and a delayed RT. In PF patients, the 1q+ is an independent factor for relapse risk and was associated with worse OS. We are completing the 6q loss assessment to determine its combined effect with 1q+ on RFS and OS. This data will be integrated into radiomics-based risk model development. References: [1] A. Ducassou et al., “Pediatric Localized Intracranial Ependymomas: A Multicenter Analysis of the Société Française de lutte contre les Cancers de l’Enfant (SFCE) from 2000 to 2013,” Int J Radiat Oncol Biol Phys, vol. 102, no. 1, pp. 166–173, 2018, doi: 10.1016/j.ijrobp.2018.05.036.[2] F. Tensaouti et al., “Patterns of failure after radiotherapy for pediatric patients with intracranial ependymoma,” Radiotherapy and Oncology, vol. 122, no. 3, pp. 362–367, 2017, doi: 10.1016/j.radonc.2016.12.025.[3] KW. Pajtler, et al., “Molecular Classification of Ependymal Tumors across All CNS Compartments, Histopathological Grades, and Age Groups”. Cancer Cell. 2015 May 11;27(5):728-43. doi: 10.1016/j.ccell.2015.04.002. Keywords: Ependymoma, pediatric, molecular type Digital Poster Highlight 961 Local Failure following flank irradiation for Wilms tumour: The Royal Marsden Experience Intan Hamid 1 , Henry C Mandeville 1 , Sam Wong 1 , Sucheta Vaidya 1 , Lynley Marshall 1 , Bruce Okoye 2 , Katherine Burnand 2 , James Talbot 3 , Vincent Khoo 4 1 Children and Young People's Unit, Royal Marsden Hospital, Sutton, United Kingdom. 2 Paediatric Surgery Unit, St George's Hospital, London, United Kingdom. 3 Radiotherapy Unit, Royal Marsden Hospital, Sutton, United Kingdom. 4 Urology, Royal Marsden Hospital, London, United Kingdom Purpose/Objective: Highly conformal Volumetric Modulated Arc Therapy (VMA)T for flank irradiation in Wilms tumour (WT) was adopted in 2017. VMAT irradiation of the tumour bed can facilitate relative sparing of the organs of interest such as spleen and contralateral kidney, to higher radiotherapy doses, thus potentially reducing the risk
Centre Alexis Vautrin, Vandoeuvre, Nancy, France. 15 Pathological Anatomy and Neuropathology, La Timone Hospital, Aix-Marseille University, Marseille, France. 16 Research, CNRS-UMR 7051, Institut de Neurophysiopathologie, Marseille, France. 17 Neuropathology, GHU Paris-Psychiatrie et Neurosciences, Saint-Anne Hospital, Paris, France. 18 Pathology, Toulouse University Hospital, Toulouse, France. 19 Research, Toulouse University , Inserm, CNRS, Centre de Recherches en Cancérologie de Toulouse7, Cancer Research Center of Toulouse, Toulouse, France. 20 Clinical Research and Innovation, Centre Léon Bérard, Lyon, France. 21 Pediatric OnInstitut d'Hématologie et d'Oncologie Pédiatrique, Centre Léon Bérard, Lyon, France Purpose/Objective: Ependymoma (EPN) is an aggressive pediatric brain tumor, with a 5-year overall survival (OS) rate of 71.4% and relapse-free-survival (RFS) rate of 50.4% [1]. Despite surgery and radiotherapy (RT), relapses occur mainly locally [2]. The goal of this study was to determine the key determinants of OS and RFS in these patients, incorporating the molecular classification [3]. Material/Methods: Throughout the period 2000-2021, 318 patients aged ≤ 22 years were retrospectively analyzed from the 15 French pediatric RT reference centers. All medical records were reviewed for clinical data extraction. Regarding molecular classification, a subset of 260 patients was specifically analyzed, accounting for the biological material (initial or relapsed tumor) from which the chromosomal alterations were assessed. Results: Median age at start of focal RT was 4 years (1.0; 22.0). Tumors were mainly in posterior fossa (PF) (70.4%). There was a majority of PF-A EPN subtype (PFA-EPN) (63.07%). Regarding treatment, 89.1% of patients underwent gross total resection, 72.3% received photon therapy (XRT) vs. 24.8% proton beam therapy (PBT) and 2.8% a mix of PBT and XRT, 53.5% received a dose ≥ 59.4 Gy. Of the 148 (46.5%) relapses, 60.3% were local, 27.4% distant and 12.3% combined. The median follow-up was 105.4 months (95% confidence interval (CI) 96.7-113.9). The 10-year OS and RFS were respectively 69.9% (CI 63.6- 75.3), and 49.6% (CI 43.4- 55.5). Multivariate analyses showed that grade 3 (p<0.01) and RT dose ≤ 54 Gy (p=0.04) were associated with lower RFS. Younger age at RT (p=0.01), lateralized tumors (p=0.02), incomplete surgery (p<0.01), time first surgery-RT ≥ 6 months (p=0.01) and grade 3 (p=0.02) were associated with lower OS. Cumulative incidence analysis showed that RT dose ≤ 54 Gy (p=0.02), grade 3 (p<0.01) and XRT (p=0.04), were associated with higher risk of local relapse, this result can be attributed to the changes in therapeutic
of late side effects. Material/Methods:
A retrospective review of all patients completing flank irradiation for WT at The Royal Marsden from April
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