S1024
Clinical – Paediatric tumours
ESTRO 2026
subgroup of patients. Material/Methods: Children between the age of 3-16 years with molecularly classified WNT-subgroup medulloblastoma and rigorously-define low-risk disease (residual <1.5 cm2 and no metastatic spread) were accrued on this prospective phase 2 clinical trial (NCT04474964) after written informed consent/assent. Patients were treated with CSI to a dose of 18Gy/10 fractions plus focal boost of 36Gy/20 fractions for a total tumor-bed dose of 54Gy/30 fractions over 6- weeks. All patients were treated using conformal photon radiotherapy techniques on a 6MV linear accelerator. Following completion of radiotherapy, all children also received 6-cycles of standard multi-agent systemic chemotherapy as per institutional practice. Time-to-event data was analysed using Kaplan-Meier method and expressed as 3-year survival outcomes. Results: Between January 2021 to July 2025, a total of 23 children (13 boys and 10 girls) with a median age of 11 years (range 5-16 years) were treated on the study. All children tolerated the treatment well and completed the planned protocol therapy. The pattern of failure included metastatic relapse involving the periventricular/ependymal in the supratentorial brain in one patient a 22 months and marginal relapse (local tumor-bed) in one child at 17 months from index diagnosis. The child with metastatic relapse progressed despite salvage chemotherapy and second course of CSI succumbing to further disease progression. The child with marginal relapse was salvaged successfully with chemotherapy followed by focal re-irradiation. At a median follow-up of 25 months (interquartile range 15-34 months), the 3-year Kaplan-Meier estimates (Figure 1) of progression free survival (PFS) and overall survival were 86% (95% confidence interval 77-94%) and 86% (95% confidence interval 73-99%) respectively.
Conclusion: Low dose CSI plus focal boost followed by adjuvant systemic chemotherapy is safe with acceptably good medium-term survival in low-risk WNT-pathway medulloblastoma. The impact of de-escalated CSI on functional outcomes still needs to be evaluated on longer follow-up. Keywords: WNT, medulloblastoma, CSI
Proffered Paper 4530
Conventionally Fractionated Re-irradiation for Recurrent Pediatric Ependymoma: Long-term Results Thomas E Merchant 1 , Hannah M Worrall 1 , Shengjie Wu 2 , Yimei Li 2 , Valerie J Groben 1 , Elizabeth A Burgen 1 , Haley M Ruleman 1 , Raja B Khan 3 , David W Ellison 4 , Paul Klimo 5 1 Radiation Oncology, St. Jude Children's Research Hospital, Memphis, USA. 2 Biostatistics, St. Jude Children's Research Hospital, Memphis, USA. 3 Neurology, St. Jude Children's Research Hospital, Memphis, USA. 4 Pathology, St. Jude Children's Research Hospital, Memphis, USA. 5 Neurosurgery, St. Jude Children's Research Hospital, Memphis, USA
Purpose/Objective: Reirradiation is a treatment for children and
adolescents with recurrent ependymoma who have previously undergone surgery and focal irradiation. This study evaluated the long-term benefits and risks of a second course of radiotherapy, patient selection criteria, factors associated with progression-free
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