S1027
Clinical – Paediatric tumours
ESTRO 2026
patients with solid tumors. Historically, pulmonary metastases have been treated with systemic therapy as well as surgical resection (called metastatectomy). Stereotactic body radiotherapy (SBRT) has been explored extensively in the adult population, but data regarding the efficacy and safety of SBRT in the pediatric population remains limited. We conducted a retrospective analysis to evaluate clinical outcomes following SBRT for pulmonary metastases from solid tumors in pediatric patients. Material/Methods: This retrospective study was approved by the Institutional Review Board. Patients who were diagnosed with a solid tumor ≤ 21 years of age and received SBRT for pulmonary metastases between 2016-2025 were included in this study. All patients were treated with 3 to 5 fractions. Electronic medical records were reviewed and data on clinical characteristics and treatment characteristics, including dose and fractionation. Radiation plans and imaging at the time of progression after first SBRT was used to determine in-field and out-of-field recurrences. Follow- up information including dates of local and distant lung progression, and date of death, and toxicities based on CTCAE v5 were recorded. The primary objective of this study was to characterize cumulative incidence of local lung progression. Secondary objectives were to characterize distant lung recurrence free survival and overall survival (OS), and toxicity of SBRT in the pediatric population. Local control was calculated using death as a competing risk. Survival was estimated using Kaplan-Meier Method. Results: Fourteen patients received their first SBRT at dose of 30-55 Gy in 3-5 fractions. Median age at SBRT was 16.5 years (range: 7.9-22.7). The most common primary histologies were osteosarcoma (n=7) and Ewing sarcoma. One patient had prior whole lung irradiation for Ewing sarcoma. No grade > 3 adverse events were observed. Two patients had grade 2 pneumonitis. With median follow up of 32.4 months (range: 4.0-94.1), 24- month cumulative incidence of local lung progression, distant lung recurrence free survival, and OS were 30.5%, 14.3%, and 61.9%, respectively. Of the patients with local lung progression, 3 patients received 30 Gy / 3 fractions and 2 patients received 50-55 Gy / 5 fractions. Conclusion: While SBRT for pulmonary metastases in pediatric patients is safe, patients remain at risk of in-field and out-of-field lung progression. These results may reflect the radioresistant nature of sarcoma histologies and the lower doses of SBRT used for pediatric patients. Further research with larger cohorts is needed to help define the optimal dose and fractionation for lung SBRT in pediatric patients. References:
Conclusion: In this series, RT achieved clinical improvement in most patients, with survival outcomes comparableto previously published data. While neither clinical nor radiological early response was statisticallyassociated with prolonged OS, the high proportion of responders and limited cohort size restrict thestrength of conclusions. These findings highlight RT’s consistent symptomatic benefit in DIPG andunderscore the need for multicenter prospective studies with standardized response assessment toclarify the prognostic role of early post-RT response Keywords: DIPG, response, survival Digital Poster 5206 Clinical Outcomes after Stereotactic Body Radiotherapy for Pulmonary Metastases in the Pediatric Population Matthew J Thoonkuzhy, Hesham Elhalawani, David Kozono, Raymond Mak, Daphne A Haas-Kogan, Kevin X Liu Radiation Oncology, Dana-Farber Cancer Institute, Boston, USA
Purpose/Objective: Pulmonary metastases occur in 10-40% of pediatric
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