ESTRO 2025 - Abstract Book

S758

Clinical - CNS

ESTRO 2025

Göttingen, Göttingen, Germany. 5 Radiation Oncology, Kreiskliniken Herford-Bünde AöR, Herford, Germany. 6 Radiation Oncology, University hospital Gdansk, Gdansk, Poland. 7 Radiation Oncology, Hospital Metropolitano de Santiago HOMS, Santiago, Dominican Republic. 8 Radiation Oncology, Radioonkologie im Vosspalais, Berlin, Germany. 9 Radiation Oncology, SANADOR, Bucharest, Romania. 10 Radiation Oncology, Klinikum Stuttgart, Stuttgart, Germany. 11 Radiation Physics, University of Minnesota, Minnesota, USA. 12 Radiation Oncology, Saudi German Hospital Cairo, Cairo, Egypt. 13 Radiation Oncology, University of Kragujevac, Kragujevac, Serbia. 14 Radiation Oncology, Austin Health, Austin, Australia. 15 Radiation Oncology, Basaksehir Cam ve Sakura Sehir Hospital, Istanbul, Turkey. 16 Radiation Physics, Hamad Medical Corporation, Doha, UAE. 17 Radiation Physics, Saint Annes Hospital, Massachussets, USA. 18 Radiation Oncology, Acibadem University School of Medicine, Istanbul, Turkey. 19 Radiation Oncology, Universit hospital Bonn, Bonn, Germany Purpose/Objective: High-grade glioma treatment usually involves radiochemotherapy, which aims to maximize tumor control. This has to be balanced with the aim of minimizing side effects e.g. cognitive side effects caused by radiation exposure to the limbic system. This international study investigates the interinstitutional variability in dose distribution to the limbic system in one given patient and evaluates the trade-offs involved in sparing these structures, focusing on the potential impact on other organs at risk (OARs), planning target volume (PTV) coverage, dose spillage, and conformity index (CI). Material/Methods: Fifty-two institutions (Fig. 1) were given an identical anonymized planning CT scan of a patient with high-grade glioma in the right parietal lobe. Pre-delineated target volume according to Sorce et. al (1) of the limbic (including CTV and PTV) as well as standard OARs (including Hippocampus ipsi- and contralateral) were included alongside detailed information on treatment required treatment planning conditions and dose constraints. Treatment plans were generated using IMRT or VMAT techniques, with optional non-coplanar beams. Each institution generated a treatment plan with a prescribed dose of 2 Gy ad 60 Gy with D 98% ≥ 98% and D 1% < 105% to the PTV. All plans underwent central review and additional limbic system structures including Temporal lobe, Fornix, Gyrus cinguli, Thalamus, Hypothalamus, Amygdala, Septum pellucidum ipsi- and contralateral were defined.

Fig. 1