ESTRO 2025 - Abstract Book

S1651

Clinical – äediatric tumours

ESTRO 2025

Results: Eighteen patients were treated in definitive (7), adjuvant (7), or neoadjuvant (4) settings. Two patients were diagnosed with Li-Fraumeni syndrome and NF1. Tumor types included Alveolar (9), Embryonal (8), and Spindle cell (1). Median clinical target volume was 162cc and a median dose 54 GyRBE was delivered (range: 41.40 - 63.01). All patients completed their treatment without interruptions. Median FU was 21 months. At 2 years LC, PFS and OS were 83.3%, 59.3%, and 93.3%, respectively (Figure 1). One patient died of metastatic disease 3 months after PT, and two recurrences were found, both occurring outside the treatment field. Acute toxicities were generally mild, with no events > G2 reported. At the 6-month follow-up, late effects were observed in four patients: one with an oropharyngeal primary developed vertigo and mild trismus (G1); two patients with parameningeal sites developed cranial nerve VI and VII weakness (G2) and otitis (G2); and one patient with a paraspinal site developed scoliosis (G2).

Conclusion: The favorable sites showed a better outcome, as reported in the literature. Proton therapy is the optimal treatment choice for children with RMS. It is well tolerated, even when combined with concomitant chemotherapy, and helps avoid both acute toxicities and late complications

Keywords: Particle therapy/Pediatric RT/Soft tissue sarcoma.

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Digital Poster Local control and toxicity profile of proton therapy in national pediatric Ewing Sarcoma cohort Sofia Paola Bianchi 1 , Petra Mozes 1 , Ulrike Mock 1 , Birgit Flechl 1 , Matthias Stephan Moll 1 , Robert Savary Malyapa 1 , Piero Fossati 1,2 , Leonie Brodbek 3 , Antonio Carlino 3 , Eugen Hug 1 , Carola Lütgendorf-Caucig 1 1 Department of Radiation Oncology, MedAustron Center for Ion Therapy, Wiener Neustadt, Austria. 2 Department of Basic and Translational Oncology and Hematology, Karl Landsteiner University of Health Sciences, Krems an der Donau, Austria. 3 Department of Medical Physics, MedAustron Ion Therapy Center, Wiener Neustadt, Austria Purpose/Objective: Ewing sarcoma is a rare bone cancer primarily affecting children, adolescents, and young adults, The optimum treatment for local disease control in Ewing sarcoma patients is still under debate. Proton therapy (PT) plays a crucial role in the treatment of these tumors, offering precision that minimizes damage to surrounding healthy tissues. This retrospective study aims to describe the treatment strategies used at our center and evaluate the local control (LC) and long-term safety.