S514
Clinical - Haemotology
ESTRO 2026
1 Department of Radiation Oncology, University of Leipzig Medical Center, Leipzig, Germany. 2 Comprehensive Cancer Center Central Germany, University of Leipzig Medical Center, Leipzig, Germany. 3 Department of Radiation Oncology, University Hospital Göttingen, Göttingen, Germany. 4 Department of Radiation Oncology, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany. 5 German Cancer Consortium (DKTK), Partner site Berlin, a partnership between DKFZ and Charité – Universitätsmedizin Berlin, Berlin, Germany. 6 Department of Radiation Oncology, Health and Medical University Potsdam, Potsdam, Germany. 7 Department of Radiation Oncology, University of Leipzig Medical Center, Münster, Germany. 8 Department of Radiation Oncology, Münster University Hospital, Münster, Germany. 9 Department of Radiation Oncology, University Hospital Tübingen, Tübingen, Germany. 10 Department of Radiation Oncology, UniUniversity Medical Center Mannheimversity of Leipzig Medical Center, Mannheim, Germany. 11 Department of Radiation Oncology, Medical Center – University of Freiburg, Freiburg, Germany. 12 Department of Radiotherapy, Hannover Medical School, Hannover, Germany. 13 Department of Radiation Oncology, UKlinikum Rechts der Isar, School of Medicine, Technical University of Munichniversity of Leipzig Medical Center, München, Germany. 14 3rd Medical Department, Klinikum Rechts der Isar, School of Medicine, Technical University of Munich, München, Germany. 15 Department of Medicine I, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany. 16 Department of Radiation Oncology, Klinikum Rechts der Isar, München, Germany Purpose/Objective: Primary central nervous system lymphoma (PCNSL) is rare but aggressive. Use of whole-brain radiotherapy (WBRT) as part of treatment has declined due to dose- dependent neurotoxicity. Comparative outcome data regarding different doses of WBRT and the influence of boost concepts are lacking. Material/Methods: Data from a multicenter registry of the German Society of Radiation Oncology's Neuro-Radio-Oncology Working Group (DEGRO AG-NRO) were analyzed. Patients treated for PCNSL between 2007 and 2023 who received and completed WBRT at any time during their disease were included. Uni- and multivariable analyses were performed to compare overall survival (OS) and progression-free survival (PFS) after radiotherapy (RT) between WBRT with doses of 20–<30 Gy, 30–36 Gy, and >36 Gy and between RT concepts with and without boost on macroscopic disease.
Results: One hundred sixty-six patients from nine centers were included, the detailed treatment concept was available from 164 patients. The median age at diagnosis was 69 years, and the median Eastern Cooperative Oncology Group Performance Status Scale (ECOG PS) was 2. Twenty-six percent of patients (n=43) received primary RT, 25% (n=41) consolidation RT, and 49% (n=80) RT for recurrent disease. Median OS after consolidating RT was 34.6 months, 7.5 months after primary RT, and 4.6 months after RT for lymphoma recurrence. Between patients treated with WBRT total dose of 20–<30 Gy, 30–36 Gy, and >36 Gy, no difference in survival was detected for primary (p=0.982), consolidation treatment (p=0.402), and treatment of recurrent disease (p=0.188, log-rank). Concerning PFS, with all treatment scenarios pooled, median PFS was not significantly different between patients in the three WBRT-groups (20–<30 Gy: 7.1 months (95% confidence interval [CI]: 0–17.7 months), 30–36 Gy: 3.6 months (95% CI: 2.7–4.4 months), >36 Gy: 7.0 months (95% CI: 2.5-11.5 months), p=0.164, log-rank). However, concerning boost application, in patients with a WBRT dose ≤ 36.0 Gy, OS was 37.3 months in patients with boost (95% CI: 21.3–53.3 months) compared to 11.0 months (95% CI: 7.7–14.3 months) in patients without boost, p=0.003. The association of prolonged survival with boost treatment persisted in multivariable Cox regression analysis. Conclusion: Survival outcomes between different WBRT doses were not significantly different. Hence, the less toxic concepts with a lower WBRT dose below <30 Gy seem advantageous. In case of macroscopic disease, boost treatments, rather than an escalated WBRT dose, appear beneficial. Keywords: PCNSL, WBRT, Boost Digital Poster Highlight 3310 EORTC survey on Global Practices in Breath-Hold Radiotherapy for Mediastinal Lymphoma Gyanne G.A. Tholen 1 , Bastiaan D.P. Ta 1 , Anne G.H. Niezink 2 , Richard Canters 1 , Dirk De Ruysscher 1 , Maaike Berbée 1 1 Department of Radiation Oncology (Maastro), GROW - Research Institute for Oncology and Reproduction, Maastricht University Medical Centre+, Maastricht, Netherlands. 2 Department of Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands Purpose/Objective: In mediastinal lymphoma (ML) patients treated with radiotherapy, a growing number of methods, such as VMAT and proton therapy, have been implemented in
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