ESTRO 2025 - Abstract Book

S1635

Clinical – äediatric tumours

ESTRO 2025

2952

Digital Poster Reported Outcomes of Intraoperative Radiotherapy (IORT) in Pediatric Oncology: expanding the benefit to pediatric patients. Maria Borrás Calbo 1 , Dolores Farga Albiol 1 , Erika Paola Romero Benavides 1 , Yolanda Real Kotbani 2 , Emilio Murcia Nadal 1 , Beatriz Geanina Cristea 1 , Francisco Javier Celada Álvarez 1 , Marian Estornell Gualde 1 , Julien Alcaide de Wandeleer 3 , Françoise Lliso Valverde 3 , Antonio Jose Conde Moreno 1 1 Department of Radiation Oncology, Hospital Universitario y Politécnico La Fe, Valencia, Spain. 2 Department of Radiation Oncology, Hospital Universitario y Politécnico La Fe, Valenica, Spain. 3 Department of Medical Phiysics, Hospital Universitario y Politécnico La Fe, Valencia, Spain Purpose/Objective: Radiotherapy (RT) plays a crucial role in the treatment of pediatric solid tumors (ST), significantly enhancing local control when combined with surgical approaches. For certain challenging cases, such as sarcomas, achieving optimal control often requires high doses of external beam radiation therapy (EBRT), which can compromise surrounding tissues—particulary concern in relapsed patients or very young children. Intraoperative radiotherapy (IORT) offers an alternative by allowing the precise delivery of a single, high-dose radiation treatment directly to the tumor bed during surgery, which may minimize collateral tissue damage and reduce long-term toxicity, making it a valuable option in complex cases. At our institution, IORT techniques are well-established for ST management in adults, and we are actively expanding its implementation as a promising therapeutic approach for pediatric patients. This study retrospectively examines our initial results using IORT as a salvage treatment for relapsed pediatric patients with solid tumors. Material/Methods: Between October 2019 and November 2024, four pediatric patients with recurrent solid tumors were treated with IORT at our center. Results: The average age at treatment was 3.5 years (range 1–5 years). All cases involved tumor recurrence. Primary tumor histologies included germ cell tumors, embryonal rhabdomyosarcoma, and neuroblastoma. All but one of the treated lesions had previously received external beam radiation therapy (EBRT) at the site of relapse. Three tumors were pelvic, and one abdominal. A single field was used for three patients, while two fields were used for one patient. The largest diameter of lesions were 1.2 cm, 2.5 cm, 4.8 cm, 6.5 cm, and 6.7 cm. IORT doses ranged from 12 to 15 Gy, applied at varying depths based on tumor characteristics (15–25 mm). Beam energies between 6 and 10 MeV were used, with shielding applied in all cases to protect surrounding tissues. No immediate post-treatment complications were observed. Conclusion: IORT shows promise as a safe, feasible option for challenging pediatric cases, though our experience remains very limited. Supported by existing literature, our goal is to continue expanding its use in selected future cases. However, further evidence is needed to determine whether a single fraction of IORT is sufficient for achieving optimal treatment outcomes in these patients.

Keywords: IORT, solid tumors, pediatric patients