S946
Clinical - Non-malignant & functional radiotherapy
ESTRO 2026
Spain. 8 Department of Oncology, University Hospital and Faculty of Medicine, Ostrava, Czech Republic. 9 Cardiovascular and Thoracic Department, Città della Salute e della Scienza Hospital, Turin, Italy. 10 Department of Radiation Oncology, University Medical Center Schleswig-Holstein, Kiel, Germany. 11 Department of Electrocardiology, Upper-Silesian Medical Center of the Medical University of Silesia, Katowice, Poland. 12 Department of Radiation Oncology, Klinikum Chemnitz, Chemnitz, Germany. 13 Department of Oncology, University of Turin, Turin, Italy. 14 Department of Radiation Oncology, Charité - University Medicine Berlin, Berlin, Germany. 15 Department of Radiation Oncology, Hannover Medical School, Hannover, Germany. 16 Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria. 17 Department of Cardiology, Amsterdam University Medical Center, Amsterdam, Netherlands. 18 Department of Cardiology, Lausanne University Hospital, Lausanne, Switzerland. 19 Department of Radiation Oncology, Medical University of Graz and LKH University Hospital of Graz, Graz, Austria. 20 Department of Radiation Oncology, Amsterdam University Medical Center, Amsterdam, Netherlands. 21 Departments of Cardiology, University Medical Centre Leiden, Leiden, Netherlands. 22 Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark Purpose/Objective: Stereotactic arrhythmia radioablation (STAR) is increasingly used to treat refractory ventricular tachycardia (VT). Evidence on safety and efficacy remains limited due to small patient cohorts. We present the interim analysis of the ongoing European STOPSTORM registry, providing multi-centre (n=26) data on STAR safety and efficacy. Material/Methods: Data from the ongoing STOPSTORM registry were extracted (24th June 2025). Patient outcomes were analysed with a focus on VT burden, (serious) adverse events (AEs), and overall survival. To account for potential delayed treatment effects, VT burden was evaluated both with and without a 6-week blanking period. AEs were graded corresponding to attributability to STAR (not/unlikely/possibly/probably related). Results: Of all individual database records (n=262), 161 patients were included after being treated with STAR for refractory VT (i.e. failed ablation and antiarrhythmic drugs) after the initiation (May 1st 2021) of the STOPSTORM.eu consortium. The median age was 69 (range: 37-91) years, 88% were male, 57% had non-ischemic heart disease, and 97% had prior catheter ablation(s) (2.5 on average). Heart failure NYHA classification was: I (11%), II (48%), III (33%), or IV
(8%). The median reduction in VT episodes per patient was 71% without and 92% with a 6-week blanking period, comparing the 6 months before and the 6 months after STAR (including 11 redo catheter ablations). Among patients who survived ≥ 6 months after STAR, 67.5% were ICD shock-free (79.2% considering the 6-week blanking period). The comparison of VT burden and related treatments before and after STAR, for patients with any reported pre-STAR episodes (n=101), is displayed without (Figure 1A) and with (Figure 1B) a 6-week blanking period.
A total of 181 AEs were reported (CTCAE version 5), 75 grade 1-2, 82 grade 3, and 24 grade 4-5, occurring in 63 individual patients (39%). Only one grade 3 SAE was probably related to STAR. Seven SAEs (five grade 3, two grade 4) were possibly related to STAR. No deaths, probably or possibly related to STAR, were recorded. The distribution of (S)AEs by grade, attributability to treatment, early vs late, and per unique patient is presented in Figure 2.
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