S388
Clinical - CNS
ESTRO 2026
radiation therapy on metastatic foci in case of expected good prognosis) in patients with multiple metastatic brain lesions. Surgery was performed on 4 patients (0.4 %) in whom we didn’t manage to differentiate between RN and disease progression 1.5- 2 years after SRS. RN was histologically confirmed in all four patients. Systemic treatment of RN consisted of GCS (16 mg per day) and, if necessary, anti-VEGF Bevacizumab 5 mg/kg. Conclusion: The difficulties in distinguishing between actual disease progression and radiation-induced changes, or their incorrect interpretation, can lead either to the premature termination of effective treatment or to the progression of neurological complications. Therefore, a multidisciplinary approach and analysis of multiparametric MRI imaging (perfusion MRI, MR spectroscopy) should become the standard of care for patients with detected brain foci. References: B.M. Ellingson, C. Chung, W.B. Pope Pseudoprogression, radionecrosis, inflammation or true tumor progression? challenges associated with glioblastoma response assessment in an evolving therapeutic landscape, J Neurooncol (2017) 134:495– 504, DOI 10.1007/s11060-017-2375-2S.B. Strauss, A. Meng, E.J. Ebani Imaging Glioblastoma Posttreatment Progression, Pseudoprogression, Pseudoresponse, Radiation Necrosis, Neuroimag Clin N Am 31 (2021) 103–120, https://doi.org/10.1016/j.nic.2020.09.010A.Zikou, C.Sioka, G.A.Alexiou, Radiation Necrosis Pseudoprogression, Pseudoresponse, and Tumor Recurrence: Imaging Challenges for the Evaluation of Treated Gliomas, Contrast Media & Molecular Imaging, Vol. 2018, ID 6828396, https://doi.org/10.1155/2018/6828396 Keywords: brain neoplasms, pseudoprogression, radionecrosis Oncological value of MRI in brain metastasis: Combining post-contrast SPACE and MPRAGE for stereotactic radiosurgery planning and follow-up Philipp Reinhardt 1 , Emre Uysal 1,2 , Daniel Schmidhalter 3 , Franca Wagner 4,5 , Ekin Ermis 1 1 Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland. 2 Department of Radiation Oncology, Prof. Dr. Cemil Tascioglu City Hospital, Istanbul, Turkey. 3 Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland. 4 University Institute of Diagnostic and Interventional Neuroradiology, Inselspital, University Hospital and Digital Poster 4042
Jul;32(4):e13062. Keywords: glioblastoma, prognostic score
Digital Poster 3896 Diagnostic challenges in differentiating early and late postradiation changes from tumor progression in brain neoplasms: impact on treatment decisions Olga Silaieva 1 , Iryna Biriuchenko 2,3 , Maksym Palii 1 1 Radiation Therapy Department, Universal Clinic "Oberig", Kyiv, Ukraine. 2 Depertment of Internal Medicine, O.O. Bogomolets National Medical University, Kyiv, Ukraine. 3 AIM, Medbase AG, Bern, Switzerland Purpose/Objective: Pseudoprogression (PsP) as well as radionecrosis (RN) are two turning points that may significantly influence the decision-making process. Radiation injury of the brain may often resemble disease progression, thus leading to unnecessary surgery or discontinuation of effective therapy. Standardized MRI imaging does not facilitate the differential diagnosis. Material/Methods: Our retrospective single-centre study included the data of patients with primary and secondary CNS malignancies between 06/2020 – 03/2025. The treatment was performed on a TrueBeam STx linear accelerator using IMRT, 3D CRT, or VMAT (RapidArc) techniques. To differentiate post-radiation changes (PsP or RN) from a true progression, contrast- enhanced MRI with MR perfusion, MR spectroscopy, and DWI were used. Results: 942 patients (53.6% females, median age 51±6.8 years) with a suspicion of progression were included in the analysis. Of those, 37.3% received stereotactic radiosurgery (SRS), 42.3% - fractionated radiotherapy (FRT), and 20.4% whole brain radiotherapy (WBRT). Median follow-up 31 months. PsP was determined in 33.6% patients with high grade gliomas (89/265), and in 9.6% of total cases (91/942), ±3 months after radiation. The incidence increased with additional concurrent chemotherapy, targeted therapy, or in the presence of MGMT promoter methylation (p<0.05 in all cases). We also found a strong positive linear correlation between the presence of PsP and relapse- free survival (r=0.78, P<0.05). The treatment of PsP included patient monitoring and, if necessary, oral GCS (4-16 mg/day).RN after SRS wasobserved in 3.9% of patients after the single fraction; the incidence increased to 18% after repeated treatments, but in both cases, no earlier than 6 months after the intervention. We also didn’t register any case of RN after WBRT (with hippocampal avoidance and boost
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