ESTRO 2025 - Abstract Book

S1570

Clinical – Mixed sites & palliation

ESTRO 2025

Keywords: SBRT, immunotherapy, targeted therapy

3903

Proffered Paper Association between severe adverse events and organ-at-risk dose in Stereotactic Arrhythmia Radiotherapy: a mid-term safety evaluation Wiert F Hoeksema 1 , Martijn H Van der Ree 1 , Jorrit Visser 2 , Claudia Herrera Siklody 3 , Joost JC Verhoeff 2 , Pieter G Postema 1 , Etienne Pruvot 3 , Brian V Balgobind 2 , Luis Schiappacasse 4 1 Department of Cardiology, Amsterdam UMC location University of Amsterdam, Amsterdam, Netherlands. 2 Department of Radiation Oncology, Amsterdam UMC location University of Amsterdam, Amsterdam, Netherlands. 3 Department of Cardiology, Lausanne University Hospital, Lausanne, Switzerland. 4 Department of Radiation Oncology, Lausanne University Hospital, Lausanne, Switzerland Purpose/Objective: Stereotactic arrhythmia radiotherapy (STAR) is a promising bail-out treatment for patients with refractory ventricular tachycardia (VT), in which radiotherapy is precisely delivered at the arrhythmic substrate. Since the heart is traditionally considered an organ-at-risk (OAR) rather than a target, detailed safety data on high-doses prescribed to the heart in relation to severe adverse events (AEs) are currently lacking but are relevant to gain insights into the safety of this potentially high-risk treatment. We sought to evaluate severe AEs of STAR in relation to the prescribed radiotherapy dose on cardiac and thoracic structures. Material/Methods: This was a bicentric study on the radiotherapy dose delivered to cardiac and thoracic structures in context of STAR for therapy-refractory VT. Patients were treated with a single fraction of 20-25 Gy using either Robotic-Guided Step and-Shoot (RGSS) or Volumetric-Modulated Arc Therapy (VMAT) technique. In all patients, photons were used with an energy beam of 6 MV. After STAR treatment, patients underwent regular follow-up according to local protocol. Additional cardiac and thoracic structures were retrospectively delineated on the planning CT-scan according to pre defined delineation instructions. Possible, probable and definite STAR- related grade ≥3 AEs were reported based on CTCAE v5.0 terminology and differences in received dose between patients with and without AEs were compared.