ESTRO 2025 - Abstract Book

S744

Clinical - CNS

ESTRO 2025

mean dose achieved within the PTV is higher (61.3Gy) compared to patients who have partially or directly relapsed outside the PTV (60.6Gy), although these differences are not statistically significant (p=0.061).

Conclusion: This analysis demonstrates that the margins recommended in the ESTRO-EANO contouring guidelines are sufficient, as most patients relapse within the same PTV volume. However, further studies would be needed to determine whether dose escalation would be feasible in this tumour type to provide the patient with greater local disease control.

Keywords: GLIOBLASTOMA; RECURRENCE; LOCAL CONTROL

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Digital Poster Re-irradiation After Re-surgery in Recurrent Glioblastoma: A Viable Strategy? Evaluating Its Role in Improving Survival Outcomes Antonella Martino 1 , Lucia Di Maio 1 , Ciro Mazzarella 1 , Silvia Mariani 1 , Nicola Dinapoli 1 , Giorgio Quintino D'Alessandris 2 , Rina Di Bonaventura 2 , Nicola Dinapoli 1 , Serena Bracci 1 , Alessio Albanese 2 , Stefania Manfrida 1 , Giuseppe Ferdinando Colloca 1 , Roberta Bertolini 1 , Silvia Longo 1 , Fabio Marazzi 1 , Fabio Allega 1 , Aida Angela Tummolo 1 , Marco Gessi 3 , Simona Gaudino 4 , Alessandro Olivi 2 , Luca Tagliaferri 1 , Valeria Masiello 1 , Alfredo Priore 1 , Maria Antonietta Gambacorta 1 , Silvia Chiesa 1 1 Radiation Oncology, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy. 2 Neurosurgery, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy. 3 Pathological Anatomy, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy. 4 Radiology, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy Purpose/Objective: Glioblastoma multiforme (GBM) IDH wild type is an aggressive brain tumor with poor prognosis and inevitable recurrence. Currently, there is no established standard of care for recurrent GBM. Meta-analyses suggest a benefit of combining radiotherapy and chemotherapy 1 ; if the patient is eligible for re-surgery, the literature supports adjuvant therapies 2 , but no evidence clarifies whether re-irradiation after re-surgery provides an additional survival advantage. This study aims to evaluate the role of re-irradiation combined with second-line systemic therapies following re-surgery, assessing its impact on overall survival (OS) and progression-free survival (PFS). Material/Methods: We conducted a retrospective study of patients aged ≥18 years with histologically confirmed GBM IDH wild type. Data from 2016 to 2023 were analyzed, during which a multidisciplinary tumor board was established. All patients underwent re-surgery for recurrent GBM, followed by various adjuvant therapies. Re-irradiation was delivered with total doses of 30–36 Gy in 10–20 fractions. Clinical outcomes, including OS and PFS after re-surgery, were assessed.