ESTRO 2025 - Abstract Book

S1465

Clinical – Mixed sites & palliation

ESTRO 2025

Results: 363 patients were treated with SBRT in the Radiation Oncology service of a level 3 hospital. 79.9% of treatments were administered in metastatic lesions, 20.1% in primary lesions. A total of 447 SBRT treatments were administered, of which 118 patients were bone SBRT (26.4%), 74 patients nodal SBRT (16.6%), 109 patients pulmonary SBRT (24.4%) and 69 patients hepatic SBRT (15.4%). Patients treated with prostate SBRT have been excluded from the analysis of results of metastatic lesions. The most used fractions were 3x11Gy (59.5%) in nodal SBRT, 2x12Gy (45.8%) in bone SBRT, variable in visceral SBRT. Median age was 60.75 years, (60.85% male, 39.15% female). LC of the disease treated with SBRT was achieved in 78.9% of the total cases. LC by location: 78.8% in bone SBRT, 81.1% in nodal SBRT, 82.6% in pulmonary SBRT and 68.1% in hepatic SBRT. The incidence of adverse effects was 5.6% (G1 – G2). No cases of G3. Conclusion: This study shows that SBRT can be considered a safe and effective treatment for LC of metastatic lesions. Prospective studies with longer follow-up are needed to clarify more accurately the role of SBRT in this type of patients. Poster Discussion Multicenter Analysis of MRI-guided, Stereotactic Body Radiotherapy as Ablative Treatment for Lymph Nodal Metastases of the Abdomen and Pelvis Jens von der Grün 1 , Sebastian Regnery 2 , Juliane Hörner-Rieber 2,3 , Inga Jessen 2 , Philipp Hoegen-Saßmannshausen 2 , Nicolaus Andratschke 1 , Stephanie Tanadini-Lang 1 , Matthias Guckenberger 1 , Annika Lattermann 4 , Dinah Konnerth 5 , Stefanie Corradini 5 , Sebastian Marschner 5 , Panagiotis Balermpas 1 1 Department of Radiation Oncology, Zurich University Hospital, Zurich, Switzerland. 2 Department of Radiation Oncology, University of Heidelberg, Heidelberg, Germany. 3 Department of Radiation Oncology, University Hospital Düsseldorf, Düsseldorf, Germany. 4 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 5 Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany Purpose/Objective: Purpose of this study was to assess efficacy and safety of magnetic resonance-imaging (MRI)-guided, stereotactic body radiotherapy (SBRT) for lymph nodal metastases (LNM) of the abdomen and pelvis. Material/Methods: This multi-center retrospective study was conducted at four institutions practicing in-room MRI-guided radiotherapy. Patients treated with MRI-guided SBRT for pelvic and abdominal LNM were enrolled. Descriptive statistics for tumor and patient characteristics were performed. Local control rates as well as progression-free and overall survival were estimated using the Kaplan-Meier method. For multivariate analyses, Cox proportional hazard were calculated. Results: A total of 161 patients with 210 lesions treated between May 2019 and October 2023 were included. Among the 26 different tumor histologies, prostate cancer (45.3%) was the most frequent. Target volume sizes varied significantly between the different anatomical sites treated (p <0.001). Patients were treated with a median dose of 35 Gy (range 25-50) in five fractions (range 3-10). With regards to the biological equivalent doses (BED) prescribed, those for metastases from prostate cancer were higher (p <0.001). Acute adverse effects of grade I, II and III were reported in 23.6%, 11.8%, and 0.6% of the patients, respectively. Two patients (1.2%) experienced grade IV gastro-intestinal Keywords: SBRT, local control, toxicity 566