S372
Clinical - CNS
ESTRO 2026
weeks) or standard (30x2Gy in 6 weeks) radiotherapy, both with concurrent and 6 cycles of adjuvant temozolomide. The primary endpoint was overall survival (OS); secondary outcomes included progression-free survival (PFS), toxicity and HRQoL, assessed by EQ-5D, QLQ-C30 and QLQ-BN20, at baseline, 1, 3 and every 3 months up to 24 months after radiotherapy. Results: Enrollment was halted early, due to poor accrual (n=129 of planned 474, 65 experimental, 64 standard). At a maximum follow-up of 24 months, median OS was shorter in the experimental arm (14 months, 95% CI 11.4-11.6), versus the standard arm (median OS not reached, p < 0.001). Median PFS was 10 vs 12 months (p=0.081). Cox regression identified treatment arm (HR 2.40, p<0.001), gross total resection (HR 0.29, p=0.004), MGMT methylation (HR 0.045, p=0.018) and age at diagnosis (HR 1.04, p = 0.009) as independent predictors of OS. Radionecrosis or pseudoprogression was reported more often in the experimental arm than in the standard arm (49% vs 24%, p=0.007). This increased occurrence of radionecrosis was independent of sex, age, MGMT-methylation, KPS, GTV and baseline steroid use. Self-reported health status (EQ-5D VAS) declined more in the experimental arm (median -2.5 [-15-8] vs 0 [-5-7], p=0.035), with a significant treatment-by-time interaction in the mixed model analysis (F(9,437)=1.908, p = 0.049). Time to
Conclusion: In the treatment of newly diagnosed glioblastoma with temozolomide-based chemoradiation, non-inferiority of hypofractionation using 6 x 6Gy, compared to the conventional 2Gy times 30 regimen, could not be demonstrated. The hypofractionation schedule is associated with inferior OS, a trend towards inferior PFS, increased reports of radionecrosis, and inferior HRQoL. Inferior HRQoL was reflected by a greater decline in self-reported health status and a shorter time to HRQoL deterioration, possibly reflecting earlier disease progression or higher rates of radionecrosis. References: 1. Stupp et al, 2005, PMID 157580092. Omuro et al, 2014, PMID 25107913 Keywords: hypofractionation, glioblastoma, radionecrosis Decision regret after treatment of brain tumor – first insights from a bicentric exploratory study Julia Reuter 1,2 , Tim Werfel 3,4 , Alexander Rühle 1,2 , Maximilian Römer 3,4 , Anja Mehnert-Theuerkauf 5,2 , Johannes Wach 6,2 , Klaus Pietschmann 3,4 , Georg Wurschi 3,4 , Nils H Nicolay 1,7 , Andreas Hinz 5,2 , Clemens Seidel 1,2 1 Department of Radiation Oncology, University Medical Center Leipzig, Leipzig, Germany. Digital Poster Highlight 2632
deterioration of EQ5D-VAS was shorter in the experimental arm (7 vs 8 months, log-rank p=0.014).
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