ESTRO 2025 - Abstract Book

S133

Invited Speaker

ESTRO 2025

Abstract:

Single-fraction stereotactic body radiotherapy (SBRT) represents a cutting-edge approach for the treatment of localized prostate cancer. Building on the favorable radiobiological profile of prostate tumors and advances in image-guided radiotherapy, this technique aims to deliver a curative dose in just one session, potentially redefining standards of care. This presentation will provide an overview of the rationale, patient selection, and technical considerations. Key elements include rigorous planning, motion management, and urethra-sparing strategies to ensure precision and minimize toxicity. Early clinical experience suggests that single-fraction SBRT is feasible and generally well tolerated in selected patients, with encouraging short-term efficacy. However, concerns about long term disease control and potential late toxicities remain, and longer follow-up is needed. Historical comparisons with single-dose brachytherapy and emerging data from prospective trials reinforce the need for careful clinical judgment before routine adoption.

4875

Speaker Abstracts Cardiac radioablation for the treatment of ventricular tachyarrhythmia Melanie Grehn Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel, Germany

Abstract: In Europe, most deaths are caused by cardiocascular diseases (45%) [1]. Patients with structural heart disease who die from sudden cardiac arrests are often afflicted by ventricular tachycardia (VT). Patients with refractory VT often undergo minimally invasive catheter ablation. However, for many patients with advanced heart disease, ablation is not an option or unauspicious as of secondary diagnoses or deep intramural substrate locations. STereotactic Arrhythmia Radiotherapy (STAR) is a new therapy option, that promises to be effective for refractory VT patients without other interventional or medicinal options [2,3]. STAR treatments are based on a complex, interdisciplinary interaction of various diagnostic procedures, as well as quality assurance (QA) methods. During the pre-planning phase, an electrophysiologist defines the VT substrate by way of electroanatomical mapping data and possibly combined with anatomical scar imaging. The defined substrate must then be transferred to the imaging data in the treatment planning system. The radiotherapy of such target is challenging due to respiratory and cardiac motion [4] and the prescription of usually 25 Gy in one fraction. Due to a small number of treated patients little is currently known about the possible acute and late radiation related effects of STAR on the whole heart or on individual substructures. Furthermore, the exact radiobiological processes in healthy as well as diseased cardiac tissue are also not yet fully understood. Though recent data suggest that STAR at lower doses (20–25 Gy) may quickly induce reprogramming of cardiac conduction, whereas radioablation at higher doses (> 30 Gy) may induce scar formation [5-8]. These different mechanisms further complicate accurate recommendations for the prescription dose, desired dose (in)homogeneity, and the maximum dose inside the target. First clinical data is promising and show VT reduction and low toxicity in those patients [9]. Meanwhile a lot of clinical trials are running all over Europe, e.g. NCT05913375, NCT05594368, NCT05439031, NCT04066517. To collect and evaluate those data a novel EU-project was funded, the Standardized Treatment and Outcome Platform for Stereotactic Therapy Of Re-entrant tachycardia by a Multidisciplinary consortium (STOPSTORM.eu consortium, Horizon 2020, GA No. 945119). The aim of this project is to establish a pooled STAR treatment database to evaluate efficacy and safety and to eventually harmonise STAR within Europe. [10] To enable harmonisation, standardisation, and optimisation of STAR treatments within the STOPSTORM.eu consortium, a comprehensive QA programme including mandatory benchmark studies (target definition and contouring of cardiac substructures, treatment planning, and delivery) and audits (treatment unit quality audits and STAR case audits) and a dedicated STAR case review software for secondary QA has been established within the