S360
Clinical - CNS
ESTRO 2026
Radiotherapy, Policlinico Umberto I, Sapienza University of Rome, Rome, Italy
Poster Discussion 1248
De-escalating RTQA in glioblastoma trials: EORTC- 1709-BTG (MIRAGE) findings support narrower margins per ESTRO-EANO guidelines Raffaella De Pietro 1 , Laure Musekera Murerwa 2 , Enrico Clementel 1 , Luiza Souza 1 , Thierry Gorlia 2 , Coreen Corning 1 , Jonas Willmann 1,3 , Joost J. C. Verhoeff ³ 4 , Orit Kaidar-Person 5,6 , André Abrunhosa-Branquinho 7 , Jaap C. Reijneveld 8 , Frederic Dhermain 9 , Coen Hurkmans 10,11 , Angelo Filippo Monti 12 , Jordi Saez 13 , Warren P. Mason 14 , Filip De Vos 15 , Ahmed Idbaih 16 , Florine Tomaszewski 17 , Michael Weller 18 , Emilie Le Rhun 19,18 , Matthias Preusser 20 , Giuseppe Minniti 21 , Patrick Roth 18 , Nicolaus Andratschke 1,3 1 Medical Department, The European Organization for
Purpose/Objective: Radiotherapy Quality Assurance (RTQA) is essential to ensure treatment consistency in multicentric trials.
While its association with outcomes has been demonstrated in several tumour sites [1], evidence in
glioblastoma remains limited. This secondary analysis of the EORTC-1709-BTG MIRAGE [2] explored whether deviations detected by RTQA were associated with patient outcomes and side effects, and whether differences emerged by QA timing (prospective vs retrospective), treatment arms or institutional experience. Material/Methods: All MIRAGE patients with RTQA-reviewed radiotherapy plans were included (n=672). Based on the Global Harmonization Group definition of deviations in delineation and/or dose delivery [3], cases were classified as protocol compliant (pC), protocol deviation per targ
Research and Treatment of Cancer (EORTC) Headquarters, Brussels, Belgium. 2 Statistics
Deparment, The European Organization for Research and Treatment of Cancer (EORTC) Headquarters, Brussels, Belgium. 3 Department of Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland. 4 Department of Radiotherapy, Cancer Center Amsterdam, Amsterdam University Medical Center, Amsterdam, Netherlands. 5 Radiation Unit, Sheba Medical Center, Tel-Hashomer, Ramat-Gan, Israel. 6 GROW, GROW – School for Oncology and Developmental Biology, Maastricht, Netherlands. 7 Serviço Radioterapia, Unidade Local de Saúde Santa Mari, Lisbon, Portugal. 8 Department of Neurology and Brain Tumor Center, Amsterdam University Medical Center, Amsterdam, Netherlands. 9 Department of Radiation Oncology, Gustave Roussy University Hospital, Villejuif, France. 10 Department of Radiation Therapy, Catharina Hospital Eindhoven, Eindhoven, Netherlands. 11 Department of Electrical Engineering and Department of Applied Physics, Technical University Eindhoven, Eindhoven, Netherlands. 12 Department of Medical Physics, ASST Grande Ospedale Metropolitano Niguarda, Milano, Netherlands. 13 Department of Radiation Oncology, Hospital Clínic de Barcelona, Barcelona, Spain. 14 Department of Medicine, Princess Margaret Cancer Centre and University of Toronto, Toronto, Canada. 15 Department of Medical Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 16 Service de Neuro-Oncologie, Institut du Cerveau (ICM), Sorbonne Université, AP-HP, Paris, France. 17 Department of Radiotherapy, ICO Rene Gauducheau, Saint-Herblain, France. 18 Department of Neurology, University Hospital Zurich, University of Zurich, Zurich, Switzerland. 19 Department of Neurosurgery, Clinical Neuroscience Center, University Hospital and University of Zurich, Zurich, Switzerland. 20 Department of Medicine I, Division of Oncology, Medical University of Vienna, Vienna, Austria. 21 Department of
et volume (pD-TV), or per organ-at-risk (pD- OAR). Endpoints were overall survival (OS),
progression-free survival (PFS), radiotherapy-related toxicity (Burden of Therapy, BoT). Kaplan–Meier and Cox models assessed survival and linear models evaluated toxicity, by compliance and RTQA timing. Analyses assessed interactions between compliance and treatment arm and centre recruitment volume. Analyses were adjusted for age, performance status, resection extent, brain-PTV mean dose. Results: Among 672 patients, RTQA compliance was pC 73.7% (495/672), pD-TV 13.6% (92/672), pD-OAR 3.4% (23/672), and pD-TV+OAR 9.2% (62/672). OS did not differ by compliance groups (log-rank p=0.10) [Figure 1]. PFS medians were ~6 months across groups (log- rank p=0.77), and BoT was comparable (global linear p=0.67) [Figure 2]. Prospective (21.3%) vs retrospective (78.7%) RTQA plans showed no association with OS or PFS (log-rank p=0.82, p=0.09, respectively). Findings were consistent across treatment arms and centre volume. Higher brain-PTV mean dose was an independent predictor of worse OS and PFS; the effect was strongest early after RT (OS time-dependent HR ≈ 1.35 per Gy) and declined over time. It was also the only factor associated with greater RT-related toxicity burden ( β >0; p=0.020).
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