S364
Clinical - CNS
ESTRO 2026
Figure 1 shows an example patient with all MRIs at all included timepoints and the resulting segmentations. Figure 2 shows longitudinal analyses for edema and enhancing tissue. Edema volumes were higher in the investigational arm shortly after RT and again after ~15 months. Enhancing volumes were higher in the investigational arm from ~16 months. Cavity volume trajectories did not differ between arms.
Conclusion: Longitudinal MRI segmentation analyses revealed distinct post-radiotherapy tissue dynamics between hypofractionated and standard chemoradiation in glioblastoma. Early and delayed edema peaks in the hypofractionated arm may reflect radiation - induced vascular injury or an inflammatory response. Enhancing tissue volumes increased at later stages, likely linked to vascular damage. However, the analysis beyond 15 months is limited because of the few remaining subjects. These radiological trajectories parallel the trial’s inferior OS and higher incidence of radionecrosis in the hypofractionated arm, suggesting a mechanistic link between fractionation regimen and tissue response. Further work will examine how imaging changes relate to the reported quality-of-life differences between the two arms. References: [1] A. Omuro et al., Clin. Cancer Res., vol. 20, no. 19, pp. 5023–5031, Sept. 2014, doi: 10.1158/1078- 0432.CCR-14-0822.[2] R. Stupp et al., N. Engl. J. Med., 2005, doi: 10.1056/NEJMoa043330.[3] M. Reuter, N. J. Schmansky, H. D. Rosas, and B. Fischl, NeuroImage, vol. 61, no. 4, pp. 1402–1418, July 2012,
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