S1004
Clinical – Paediatric tumours
ESTRO 2026
significantly over recent decades, reaching 80–85% due to better treatment. However, some childhood cancers have not seen the same improvements and their need for multimodal treatment, including radiotherapy, persists. Despite technological advances in radiotherapy, implementation in paediatric settings appears delayed compared to adults. The aim of this study was to map the technological development of radiotherapy from 2008 to 2024 to guide future research. Material/Methods: We registered and analysed data from the Danish Childhood Cancer Registry (DCCR) and data from the radiotherapy sub-registry from 2008 to 2024. Radiotherapy data included treatment technique, IGRT modality, use of motion management, fractionation, and dose per course and fraction. Patients under 18 years at diagnosis and who received radiotherapy were included (TBI not included). Photon and proton therapy plans were retrieved from national and international sources. Descriptive temporal analyses were performed using RStudio. Results: A total of 557 paediatric patients received radiotherapy. Diagnoses peaked at different ages; however, brain tumors were the most common, followed by soft tissue sarcomas and bone tumors (Fig. 1). When divided into curative ( ≤ 2 Gy/fraction) and palliative (>2 Gy/fraction) radiotherapy, this distribution persisted, although fewer diagnoses were treated with palliative intent overall. VMAT and proton therapy usage increased over time, though the transition from 3DCRT to more conformal techniques varied by diagnosis (Fig. 2). For example, conformal techniques for kidney tumors was not standard prior 2017. Moreover, palliative proton therapy was used only for soft tissue sarcomas. Daily IGRT became standard practice from the mid-2010s, with CBCT replacing other modalities. DIBH was initially applied primarily in lymphoma cases, with broader adoption across other diagnoses emerging after 2017.
Figure 2 Treatment techniques pr. Diagnoses groups, fraction dose ≤ 2Gy/F over time (years). 3DCRT: 3D includes 2D fields planned on 3D CT scans. Conclusion: This population-based cohort includes all Danish children treated with radiotherapy between 2008 and 2024. Despite widespread adoption of modern RT techniques, implementation varied across tumor types, likely due to protocol constraints and clinical caution. The findings underscore the importance of clinical trials for the safe integration of advanced technologies in pediatric radiotherapy. The DCCR radiotherapy registry enables data-driven improvements in practice and highlights the need for continued evidence generation to support technology adoption in this vulnerable population. Keywords: Radiotherapy and IGRT modalities, national cohort Digital Poster Highlight 1383 Reirradiation of paediatric patients in Denmark – an overlooked cohort? Daniella Elisabet Østergaard 1 , Bob Smulders 1,2 , Morten Høyer 2 , Morten Jørgensen 1 , Yasmin Lassen- Ramshad 2,3 , Akmal Safwat 2,3 , Lisa Lyngsie Hjalgrim 4 , Maja Vestmø Maraldo 1,5 1 Department of Oncology, University Hospital of Copenhagen – Rigshospitalet, Copenhagen, Denmark. 2 Danish Centre for Particle Therapy, University Hospital of Aarhus, Aarhus, Denmark. 3 Department of Oncology, University Hospital of Aarhus, Aarhus, Denmark. 4 Department of Children and Adolescent Medicine, University Hospital of Copenhagen – Rigshospitalet, Copenhagen, Denmark. 5 Department of Clinical Medicine, Faculty of Health, University of Copenhagen, Copenhagen, Denmark Purpose/Objective: Reirradiation is increasingly used in adults as survival improves. Paediatric patients are also offered reirradiation, and although annual case numbers per institution are small, cumulative national experience provides valuable insight. Reirradiation in children
Figure 1 Distribution of diagnoses in 5 age groups. Colors indicates diagnoses and total number of patients reported in bar plot.
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