ESTRO 2025 - Abstract Book

S1497

Clinical – Mixed sites & palliation

ESTRO 2025

1754

Proffered Paper Dose-intensified stereotactic body radiation therapy for vertebral oligometastases: results from a prospective clinical trial Matthias Guckenberger 1 , Lotte Wilke 2 , Charlotte Billiet 3 , Susanne Rogers 4 , Ciro Franzese 5 , Daniel Schnell 6 , Mateusz Spałek 7 , Daniel M. Aebersold 8 , Hossein Hemmatazad 8 , Thomas Zilli 9,10 , Judit Boda-Heggemann 11 , Brigitta G. Baumert 12 , Jean-Jacques Stelmes 10,13 , Franziska Nägler 14 , Philipp Gut 15 , Christian Weiß 16 , Alessio Bruni 17 , Frank Zimmermann 18 , Robert Förster 2,8,19 , Jörg Zimmer 20 , Indira Madani 2 1 Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland. 2 Radiation Oncology, University Hospital Zurich, Zurich, Switzerland. 3 Radiation Oncology, Iridium Netwerk, Wilrijk, University of Antwerp, Antwerp, Belgium. 4 Radio-Onkologie-Zentrum Mittelland, Kantonsspital Aarau, Aarau, Switzerland. 5 Radiation Oncology, Humanitas University, Humanitas Research Hospital IRCCS, Milan, Italy. 6 Radiation Oncology, University Hospital Freiburg, Freiburg, Germany. 7 Radiation Oncology, Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland. 8 Radiation Oncology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland. 9 Radiation Oncology, Geneva University Hospital, Geneva, Switzerland. 10 Radiation Oncology, Oncology Institute of Southern Switzerland, EOC, Bellinzona, Switzerland. 11 Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany. 12 Radiation Oncology, Kantonsspital Graubunden, Chur, Switzerland. 13 Luxemburg Health Directorate, Ministry of Health and Social Security, Luxemburg, Luxembourg. 14 Radiation Oncology, University Hospital Leipzig, Leipzig, Germany. 15 Radiation Oncology, Hirslanden Clinic, Zurich, Switzerland. 16 Radiation Oncology, Darmstadt General Hospital, Darmstadt, Germany. 17 Radiation Oncology, University Hospital of Modena, Modena, Italy. 18 Radiation Oncology, University Hospital Basel, Basel, Switzerland. 19 Radiation Oncology, Kantonsspital Winterthur, Winterthur, Switzerland. 20 Radiotherapy, MVZ, Dresden, Germany Purpose/Objective: To determine whether dose-intensified stereotactic body radiation therapy (SBRT) for vertebral oligometastases achieves long-term local metastasis control without increase in adverse events, even in high-risk patients with epidural or paraspinal involvement. Material/Methods: This trial was conducted in eighteen centers across five countries between 2016 and 2023. The trial was initiated as an open-label, multicenter, randomized, controlled phase 3 trial comparing SBRT with conventional external-beam radiotherapy for 1-2 painful stable/potentially unstable vertebral metastases. In 2018, the trial was complemented with a non-randomized arm comprising patients recognized ineligible for randomization and treated with SBRT (ClinicalTrials.gov NCT02800551). Patients from the randomized and non-randomized arms treated with SBRT for vertebral oligometastases (≤5 distant metastases in total) were included into this analysis. Patients underwent SBRT with 48.5 Gy/10 (with epidural involvement) or 40 Gy/5 (without epidural involvement). The primary outcome was cumulative incidence of local failure and vertebral compression fracture (VCF) assessed with a competing risk regression model, overall survival estimated with Kaplan-Meier method and rates of adverse events. Results: A total of 214 patients were screened for eligibility, of whom 63 were randomized and 151 were included in the non randomized arm. Of 178 patients treated with SBRT in the experimental and non-randomized arms, 128 patients with 143 vertebral oligometastases were identified and analyzed (Table 1). The median age of patients was 68 years (IQR 60-73); 77 patients (60.2%) had radiosensitive primary tumors. Twenty-three (16.1%) and 22 (15.4%) metastases had epidural and paraspinal tumor involvement, respectively. The median follow-up of all patients was 24 months (IQR 14-25). Four (2.8%) – two with paraspinal involvement and none with epidural involvement - of 142 radiologically assessed vertebral metastases developed local failure resulting in cumulative incidence of 0.8% and 5.3% at 1 and 2 years, respectively. The 1- and 2-year estimates of overall survival were 94.3% (95% CI, 90.2-98.4%) and 82.2% (95% CI, 74.9-89.6%), respectively (Fig. 1). On