ESTRO 2025 - Abstract Book

S1637

Clinical – äediatric tumours

ESTRO 2025

Conclusion: In IR plans, IMPT prevented three violations in three patients compared to VMAT. For HR treatment plans, VMAT reduced three violations in three patients and IMPT prevented eight violations in five patients compared to VMAT. The absolute dose differences between IMPT and VMAT when the doses are violated are minimal.

Keywords: Flank irradiation, VMAT, IMPT

3282

Mini-Oral Pediatric localized intracranial ependymoma: survival, prognostic factors in a French multicentric retrospective study from 2000 to 2021 (NCT05151718) Alexis Marguerit 1,2 , Fatima Tensaouti 2,3 , Mathilde Morisseau 4 , Stéphanie Bolle 5 , Xavier Mirabel 6 , Xavier Muracciole 7 , Claire Alapetite 8 , Line Claude 9 , Julie Leseur 10 , Aymeri Huchet 11 , Jérôme Doyen 12 , Georges Noël 13 , Stéphane Supiot 14 , Valérie Bernier-Chastagner 15 , Dominique Figarella-Branger 16,17 , Pascale Varlet 18 , Emmanuelle Uro-Coste 19,20,21 , Julien Gautier 22 , Pierre Leblond 23 1 Radiation oncology, Institut du Cancer de Montpellier, Montpellier, France. 2 Radiation oncology, Oncopôle Claudius Regaud, Institut Universitaire du Cancer de Toulouse, Toulouse, France. 3 Toulouse Neuroimaging Center, Université de Toulouse, Inserm, Toulouse, France. 4 Biostatistic and health data science unit, Oncopôle Claudius Regaud, Institut Universitaire du Cancer de Toulouse, Toulouse, France. 5 Radiation oncology, Institut Gustave Roussy, Paris, France. 6 Radiation oncology, Centre Oscar Lambret, Lille, France. 7 Radiation oncology, La Timone Hospital, Marseille, France. 8 Radiation oncology, Institut Curie, Paris, France. 9 Radiation oncology, Centre Léon Bérard, Lyon, France. 10 Radiation oncology, Centre Eugène Marquis, Rennes, France. 11 Radiation oncology, Centre Hospitalier et Universitaire de Bordeaux, Bordeaux, France. 12 Radiation oncology, Centre Antoine-Lacassagne, University of Côte d'azur, Nice, France. 13 Radiation oncology, ICANS, Strasbourg, France. 14 Radiation oncology, Institut de Cancérologie de l'Ouest, Nantes, France. 15 Radiation oncology, Institut de Cancérologie de Lorraine, Vandoeuvre les Nancy, France. 16 Pathological anatomy and neuropathology, La Timone Hospital, Aix-Marseille University, Marseille, France. 17 CNRS-UMR 7051, Institut de Neurophysiopathologie, Marseille, France. 18 Neuropathology, GHU Paris-Psychiatrie et Neurosciences, Saint-Anne Hospital, Paris, France. 19 Pathology, Toulouse University Hospital, Toulouse, France. 20 INSERM U1037, Cancer Research Center of Toulouse, Toulouse, France. 21 Research, Université Paul Sabatier, Toulouse III, Toulouse, France. 22 Clinical Research and Innovation, Centre Léon Bérard, Lyon, France. 23 Institut d'Hématologie et d'Oncologie Pédiatrique, Centre Léon Bérard, Lyon, France Purpose/Objective: Ependymoma (EPN) is a common brain tumor in childhood, 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 in the irradiated area[2]. The objectives of this study were to identify factors associated with OS and RFS, in pediatric ependymoma patients. Material/Methods: Between 2000 and 2021, 319 patients aged ≤ 22 years were analyzed from the 15 main French pediatric RT reference centers. Their medical records were reviewed to extract information, and 226 of them were reviewed for molecular classification. Results: Median age at diagnosis was 3 years and at start of RT it was 4 years (1.0; 22.0). Tumors were mainly in posterior fossa (71.8%). Regarding treatment, 89.1% of patients underwent gross total resection, 72.1% received photon therapy (XRT) vs. 25.1% proton beam therapy (PBT) and 2.8% a mix of PBT and XRT, 53.6% received a dose ≥59.4 Gy. Of the 149 (46.7%) relapses, 59.9% were local, 27.2% distant and 12.9% combined. The median follow-up was 105.4 months (95% confidence interval (CI) 96.7-113.9). The 10-years OS and 10-years RFS were respectively 69.7% (95% CI 63.4-