S960
Clinical - Non-malignant & functional radiotherapy
ESTRO 2026
STAR), with a 3-mm isotropic margin creating the planning target volume (PTV). A single 25 Gy fraction (prescribed to the 70–85% isodose line) was delivered via volumetric modulated arc therapy. Two patients (25%) underwent MRI-guided STAR on a hybrid 0.35T MR linear accelerator. Patients were assessed immediately after treatment, at 6 weeks, 3 months, 6 months, and annually, including ICD interrogations. We counted ICD shocks before and after STAR. For the pre-STAR phase, all events within the six months before STAR were considered. A six-week silencing (blanking) period immediately following the STAR procedure was included in the analysis. The post-STAR period was defined as the time from the end of the blanking period until each patient’s follow-up end. Results: The median age of the treated patients was 70 (67-79) years with a median ECOG of 2 (2-3) points. The majority of patients (n=5, 62.5%) had ischemic cardiomyopathy, while three patients (37.5%) had dilated cardiomyopathy. The median event-free survival was 1,6 months,, at a median follow up time of 14 (0.1-70) months. The median overall survival after STAR was 14 (0.1-70) months, the one and two-year survival was 57.1% and 28.6%, respectively (Figure 1). Among the eight patients analyzed, five showed a reduction in shock velocity after STAR, two maintained a velocity of zero, and one exhibited an increased velocity post-treatment. However, two patients did not respond and required in-patient treatment. Two patients experienced an early death, one patient refused life-sustaining treatment and one patient died of sudden pulmonary embolism probably unrelated to STAR. All other patients - except for one patient who developed a CTCAE Grade 4 pneumonitis - tolerated the treatment well.
(range 5.3–69.8; IQR 9.5–32); in 5 cases (22.7%) it lasted > 36 months (Diagram 2).
Conclusion: Pseudoprogression onset beyond 36 months was rare (1 case), but when it occurred, a considerable proportion (22.7%) persisted > 36 months. These findings may help clinicians differentiate true relapse from late-onset pseudoprogression and counsel patients regarding expected MRI evolution after radiosurgery. Keywords: Vestibular Schwannoma, SRS, SBRT Stereotactic Arrhythmia Radioablation (STAR) for Ventricular Tachycardia: Single Center Experience Maiwand Ahmadsei 1 , Maksym Fritsak 1 , Florian Wortman 1 , Stefanie Ehrbar 1 , Lotte Wilke 1 , Silvia Fabiano 1 , Stefanie Tanadini-Lang 1 , Lorraine Sazgary 2 , Corinna I.B. Brunckhorst 2 , Firat Duru 2 , Frank Ruschitzka 2 , Matthias Guckenberger 1 , Michael C. Mayinger 1 , Ardan M. Saguner 2 , Nicolaus Andratschke 1 1 Department of Radiation-Oncology, University Hospital Zurich, Zurich, Switzerland. 2 Department of Cardiology, University Hospital Zurich, Zurich, Switzerland Purpose/Objective: Stereotactic Arrhythmia Radioablation (STAR) targeting arrhythmogenic scar after cardiac electroanatomical mapping has emerged as a novel option for patients unresponsive to standard therapies of ventricular tachycardia.1,2 Here, we present our institutional experience treating eight patients with this innovative approach. Material/Methods: Eight patients with refractory sustained monomorphic Digital Poster 5162 ventricular tachycardia (smVT), unresponsive to guideline-directed medical therapy, catheter ablation(s) and antiarrhythmic drugs, were treated with STAR. Targets were defined using 4D-CT, cardiac MRI and invasive 3D electroanatomical mapping by a multidisciplinary team. Internal target volumes accounted for respiratory motion (non-MRI-guided
Conclusion: STAR shows promise as an effective palliative option in patients with therapy-refractory VT by early and clinically relevant sustained VT burden reduction. Long-term efficacy and co-morbidity remain challenging, therefore future strategies should focus on optimal patient selection and treatment optimization. References: Mayinger M, Kovacs B, Tanadini-Lang S, Ehrbar S, Wilke L, Chamberlain M, Moreira A, Weitkamp N, Brunckhorst C, Duru F, Steffel J, Breitenstein A, Alkadhi H, Garcia Schueler HI, Manka R, Ruschitzka F,
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