S1025
Clinical – Paediatric tumours
ESTRO 2026
survival (PFS) and overall survival (OS), and the potential use of craniospinal irradiation (CSI) for those with local tumor progression at the time of first recurrence. Material/Methods: Between July 6, 1994, and January 31, 2024, 150 children and adolescents with ependymoma were treated with a second course of fractionated radiotherapy at St. Jude Children’s Research Hospital. Sixty-four were enrolled in a prospective trial (RERTEP, NCT02125786) activated in 2018 and closed to accrual in 2022. Patients were included if their initial and second treatment courses included conventional fractionation to a minimum total dose of 50.4Gy and if their second course included CSI in the setting of metastatic disease. The Kaplan-Meier method was used to estimate PFS and OS, and the Cox proportional hazard model investigated the association of PFS or OS with continuous covariates. The cumulative incidence of necrosis and death from complications was calculated with competing risks. Results: The 10-year and 20-year PFS/OS estimates for the cohort were 19.45%/34.29% and 8.99%/13.13%. PFS and OS differed according to RT1 pattern of failure (Fig 1). No significant difference in progression-free (p=0.1351) or overall (p=0.2705) survival comparing patients with RT1 local failure treated with focal irradiation versus craniospinal irradiation. Necrosis was significantly greater in patients treated using protons compared to photons. Incidence of grade 3 necrosis after RT2 was 19.89% (Fig 2). The 10-year cumulative incidence of death from complications or secondary tumor was 8.48% for the entire cohort.Fig 1. PFS by RT1 pattern of failure.
Legend: Grade 1 – no treatment, Grade 2 – dexamethasone, Grade 3 – hyperbaric oxygen/ bevacizumab. Conclusion: A second course of conventionally fractionated radiotherapy can prolong survival for children and adolescents with recurrent ependymoma, though the prognosis remains poor. Patients with combined local and distant failure, early tumor progression after initial treatment, and adverse molecular features had the worst outcomes. CSI did not significantly improve PFS or OS for patients with RT1 local failure compared to focal irradiation. The risk of necrosis, especially with proton therapy, underscores the need for careful patient selection and follow-up. Future research should explore advanced radiation techniques, hypofractionation, and concurrent therapies to improve outcomes and reduce complications. Keywords: Re-irradiation, ependymoma, necrosis Digital Poster 4680 Clinical Outcomes of Stereotactic Body Radiotherapy (SBRT) for Extracranial Metastases in Pediatric Malignancies Zeynep Güral 1 , Senay Mutaf Geçgel 1 , Ayça İ riba ş Çelik 2 , Erkin Akyüz 2 , Serap Yücel 1 , Fulya A ğ ao ğ lu 1 1 Radiation Oncology, Acibadem Mehmet Ali Aydınlar University, İ stanbul, Turkey. 2 Radiation Oncology, İ stanbul University Faculty of Medicine, İ stanbul, Turkey Purpose/Objective: Stereotactic body radiotherapy (SBRT) in pediatric malignancies offers precise, high-dose radiation delivery to tumors while minimizing exposure to surrounding healthy tissues—an important consideration in preventing adverse effects on growth and development. The use of SBRT in pediatric oncology has been increasing; however, clinical data and outcome reports remain limited. This study aimed to evaluate local control (LC), progression-free survival (PFS), overall survival (OS), and toxicity rates following SBRT in pediatric patients with extracranial
Fig 2. Cumulative incidence of necrosis by grade.
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