S371
Clinical - CNS
ESTRO 2026
experiencing a significant PD and 11% experiencing pseudoprogression. Keywords: radiosurgery, cerebellopontine angle tumours
Digital Poster 2228 Local control after stereotactic radiosurgery and fractionated stereotactic radiotherapy for cerebellopontine angle tumours Ł ukasz Raszewski, Agnieszka Lewandowska, Adam Deja, Paulina Kujawa, Krystyna Adamska Radiotherapy Department, Greater Poland Cancer Centre, Pozna ń , Poland Purpose/Objective: Stereotactic radiotherapy of cerebellopontine angle tumours (CATs) is an upfront strategy for symptomatic or progressive CATs resulting in a high local control (LC) and acceptable toxicity when compared to neurosurgical treatment. The aim of this study is to report a single institution experience in irradiating CATs with an emphasis on LC after stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) and to compare the progression and pseudoprogression rates after both interventions. Material/Methods: 83 patients (54 women and 29 men; respectively 65,1% and 34,9%) with radiologically diagnosed CATs were treated using CyberKnife between 2016 and 2022. 64 patients (58,7%) with Koos grade I and II tumours received SRS treatment with a median dose of 12 Gy (range: 11-13 Gy) for an 80% isodose, while 43 patients (41,3%) with Koos grade III and IV tumours received fSRT with a median dose of 18 Gy in 3 fractions of 6 Gy (range: 3-5 fractions; 18-25 Gy total dose) on an 80% isodose. Treatment response and LC was monitored with an annual contrast-enhanced head magnetic resonance imaging (MRIs). Progression (PD) was defined as any increase of diameter of irradiated CATs in follow-up MRIs. The study included patients with at least 3 years of follow-up (range: 36 – 108 months). Results: During the follow-up 25 patients (30% of all patients) presented a partial response (PR), while 45 patients (54%) remained stable (SD). PR was more common in SRS group (32%) when compared to fSRT group (27%), however the difference was not statistically significant. A radiological PD was reported in 13 patients (16%), with 11 cases (86%) reported within first two years after the treatment. However, among the patients who experienced a radiological PD only 4 patients (5% of all patients) had a PD in two or more consecutive MRIs or required a neurosurgical intervention, while the rest of initially PD tumours in next MRIs remained SD (2 patients) or PR was reported (7 patients). There were no significant differences in PD rates between SRS and fSRT. Overall LC at 3 years and 5 years after irradiation were respectively 95% and 90%. Conclusion: Both SRS and fSRT provided an excellent local control after irradiating CATs with only 5% of patients
Proffered Paper 2249 Final results of a nationwide multicenter randomized trial (GOLD) on hypofractionated chemoradiation for glioblastoma: survival and HRQoL Anouk M. de Jong 1,2 , Arthur T.J. van der Boog 1,2 , Gerda Wester 3 , Danielle B.P. Eekers 4 , Tom C.G. Budiharto 5 , Tom Rozema 6 , Mariska A.E. van de Sande 6 , Frank J Lagerwaard 7 , Anna M.E. Bruynzeel 7 , Crystal de Groot 8 , Matthijs van der Meulen 9 , Fia Cialdella 1,2 , Jan-Willem Dankbaar 10 , Jeroen Hendrikse 10 , Karin E Kleynen 1 , An Claes 1 , Mariëlle E.P. Philippens 1 , Ernst Smid 1 , Filip Y.F.L. de Vos 11 , Pierre A. Robe 2 , Szabolcs David 7 , Tom J. Snijders 2 , Joost J.C. Verhoeff 7 1 Radiation Oncology, University Medical Center Utrecht, Utrecht, Netherlands. 2 Neurology and Neurosurgery, University Medical Center Utrecht, Brain Center, Utrecht, Netherlands. 3 Radiation Oncology, RadiotherapieGroep, Arnhem, Netherlands. 4 Radiation Oncology (MAASTRO), GROW School for Oncology and Reproduction, Maastricht University Medical Centre, Maastricht, Netherlands. 5 Radiation Oncology, Catharina Hospital, Eindhoven, Netherlands. 6 Radiation Oncology, Instituut Verbeeten, Tilburg, Netherlands. 7 Radiation Oncology, Amsterdam University Medical Center, Amsterdam, Netherlands. 8 Radiation Oncology, Isala Clinics, Zwolle, Netherlands. 9 Neurology, Leiden University Medical Center, Leiden, Netherlands. 10 Radiology, University Medical Center Utrecht, Utrecht, Netherlands. 11 Medical Oncology, University Medical Center Utrecht, Utrecht, Netherlands Purpose/Objective: In glioblastoma, standard chemoradiation since the EORTC/NCIC trial of 2005 consists of 30x2Gy with concurrent and adjuvant temozolomide1. A prior study suggested that extreme hypofractionation (6x6Gy) may offer comparable survival2, with reduced treatment time and costs, potentially improving health-related quality of life (HRQoL). This phase III randomized trial (registered at Netherlands Trial Register, trial-ID NL72953.041.20) evaluated non- inferiority of hypofractionated temozolomide chemoradiation in glioblastoma patients, both for
survival and HRQoL. Material/Methods:
Adults with newly diagnosed glioblastoma and a Karnofsky performance status (KPS) ≥ 70 were randomized (1:1) to hypofractionated (6x6Gy in 2
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