ESTRO 2022 - Abstract Book

S901

Abstract book

ESTRO 2022

Utrecht, The Netherlands; 4 University Hospital of Zurich, Department of Radiation Oncology, Zurich, Switzerland; 5 Leiden University Medical Center, Unit of clinical Electrophysiology, Leiden, The Netherlands; 6 Maria Sk ł odowska-Curie National Research Institute of Oncology, Department of Radiotherapy, Gliwice, Poland; 7 Azienda Unità Sanitaria Locale – IRCCS, Bioethics Unit, Reggio Emilia, Italy Purpose or Objective In patients with structural heart disease, ventricular tachycardia (VT) plays a decisive role in sudden cardiac death. VT patients are often treated with ICDs, anti-arrhythmia medication and catheter ablation. For refractory patients, STereotactic Arrhythmia Radioablation (STAR), to the underlying VT substrate has recently been introduced and showed promising results for otherwise untreatable patients. The purpose of the STOPSTORM consortium (EU-Horizon-2020 GA-No. 945119) is to harmonize and optimize STAR in several work-packages. Therefore to obtain an overview of ongoing trials, as well as the contents of the respective quality assurance programmes regarding stereotactic radiotherapy treatments and specifically for the performance of STAR, the consortium members had to fill a questionnaire. Materials and Methods The STOPSTORM consortium consists of 31 members including 24 electrophysiology and 22 radiation oncology departments performing or participating in STAR throughout eight European countries. To obtain initial overview of organization, equipment, standards, procedures, experiences and quality levels for SBRT and STAR, a detailed survey with open questions for electrophysiology (18 questions), radiation oncology (24 questions) and medical physics (23 questions) was circulated among STOPSTORM members. Results All clinics participating in STOPSTORM completed the survey. Catheter ablation for VT (20/24 centres ≥ 20 p.a.) and SBRT (13/22 centres > 200 p.a.) experience is high and technical equipment is state-of-the-art. 16 centres performed a total of 84 STAR treatments until May 2021 and 11 centres already participate in clinical trials for STAR. Target volume definition is based on electroanatomical mapping during VT (23), pace mapping (18), reduced voltage areas (15) and/or late ventricular potentials (18). Half of the centres therefore include the clinical VT areas, while the other half include the whole arrhythmogenic substrate. 18 and 4 centres use 4D-CT-ITV or tracking/gating concepts for respiratory and 10 vs. 10 centres use ECG-triggered-4D-CT or statistical margins for cardiac motion management, respectively. In all but one clinic, a dose of 25 Gy in a single fraction is applied. The prescription method, inhomogeneity in the PTV and planning technique however varies greatly. 13/22 centres report technical system audits every 1-2 years, while regular dose audits are performed in 16/22 centres. 17/22 centres perform end-to-end tests specifically for SBRT. All centres perform patient-specific plan verifications for STAR, but with various evaluation criteria. A summary of various survey results is given in figure 1.

Conclusion Experience with catheter ablation, SBRT and STAR within the STOPSTORM consortium is adequate, while the survey clearly showed areas of harmonization and optimization need for target delineation, motion management, dosimetry and quality assurance which will be addressed in the STOPSTORM project work-packages.

PO-1066 Impact of linac design on patient perception of radiotherapy treatment

V. Reyes López 1 , D. García Relancio 1 , A. Palma Evans 1 , M. Altabas González 1 , A. Giraldo Marin 1 , R. Granado Carrasco 1 , B. Pérez Esteve 1 , G. Gálvez Hernando 2 , M. Hermida López 3 , A. Varó Curbelo 3 , X. Maldonado Pijoan 1 , J. Giralt López de Sagredo 1