Stereotactic Arrhythmia Radioablation in Europe-Treatment Planning Benchmark Results of the STOPSTORM. eu Consortium

Purpose/Objective(s)In patients with refractory ventricular tachycardia (VT), Stereotactic Arrhythmia Radioablation (STAR) showed promising results for otherwise untreatable patients. The STOPSTORM.eu project coordinates European efforts to clinically validate STAR and to refine protocols and guidelines. The aim of this work is to present the current clinical STAR practice in Europe based on three examples as baseline for further optimization.Materials/MethodsTarget Volumes (TV) and Organs-at-Risk (OAR) were generated from previous consortium benchmarks and consensus definitions for three well-selected STAR cases. Planning Target Volumes (PTV) were generated based on three different compensation strategies for cardiac and respiratory motion and overlapped/close OARs like coronary arteries or stomach. The STOPSTORM.eu members were asked to generate single fraction treatment plans with 25 Gy dose prescription based on ICRU report 91 for each case based on their STAR clinical practice through multi-disciplinary discussion. Resulting dose distributions were analyzed independently using a customized platform for multi-center treatment planning studies.ResultsBy November 2021, 20 centers submitted 22, 23 and 22 treatment plans for case 1, 2 and 3, respectively, mostly (75% of plans) using Intensity Modulated Arc Therapy (IMAT) with 6 MeV FFF beams (73% of the IMAT plans) among other commonly used techniques for stereotactic radiotherapy. Presently, used guidelines for STAR treatment planning and OAR dose limits vary greatly and are mostly based on the AAPM TG-101 report and RAVENTA trial publication. As a major finding, 73% of the submitted plans showed close OAR sparing overachieving high PTV coverage (Figure 1 and Table 1) arguing that lower doses may also result in clinical efficiency. Cases 1 and 3 dose distributions (referenced as A. and C. in Figure 2) highlighted how OARs sparing also resulted in heavy PTV under dosing for some participants.ConclusionFrom this first STOPSTORM.eu multi-center/multi-platform treatment planning benchmark study we obtained important information concerning current clinical practice from major European centers performing Stereotactic Arrhythmia Radioablation for VT. With the strongly varying approaches of the centers as basis, the key task for the STOPSTORM.eu project is to find consensus, aiming to harmonize and optimize STAR practice in Europe.