ESTRO 2022 - Abstract Book

S1232

Abstract book

ESTRO 2022

Conclusion Our series show that (stereotactic body) radiotherapy for oligoprogressive disease during PD1-inhibition can induce long- term disease control and overall survival. Although abscopal effects were suspected in 3 patients, they were not confirmed with volumetric assessment in 2 patients. The discrepancy found between one-dimensional and volumetric response assessment argues for including volumetric assessment in further studies.

PO-1452 Stereotactic ablative radiotherapy in patients with refractory ventricular tachyarrhythmia

L. Nicosia 1 , N. Giaj-Levra 1 , G. Sicignano 2 , F. Cuccia 1 , V. Figlia 1 , R. Mazzola 1 , F. Ricchetti 1 , M. Rigo 1 , C. Vitale 1 , G. Attinà 1 , A. De Simone 1 , D. Gurrera 1 , R. Ruggeri 1 , G. Molon 3 , F. Alongi 1 1 IRCCS Ospedale Sacro Cuore Don Calabria, Advanced Radiation Oncology Department, Negrar, Italy; 2 IRCCS Ospedale Sacro Cuore Don Calabria, Advanced Radiation Oncology Department, IRCCS Ospedale Sacro Cuore Don Calabria, Negrar Di Valpolicella, Italy., Negrar, Italy; 3 , Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Ospedale Sacro Cuore Don Calabria, Cardiology Department, Negrar, Italy Purpose or Objective The current management of refractory ventricular tachycardia (RVT) is represented by catheter ablation. Nevertheless, this cardiological procedure is associated with a risk of complication and some patients are not eligible. Recently, initial clinical experiences are exploring the role of stereotactic arrythmia radioablation (STAR) as an emerging alternative approach in selected patients. Nevertheless, a standardized method to deliver ablative doses to the heart is not yet available and several questions are still under debate, including: diagnostic radiological exams, target delineation, organ motion management, efficacy and safety. In the present study, we reported the preliminary results about the role of STAR in the management of patients with RVT. Materials and Methods Patients with a diagnosis of RVT, excluded from other cardiological procedures, were defined as eligible to STAR. All patients should receive a 3D Electroanatomic Mapping, a cardio-CT scan and cardiac 18F-fluoro-2-deoxy-D-glucose positron emission tomography (18FDG – PET scan) in order to identify the ventricular target pathological area. Cardiac MR was offered only in patients with a defibrillator compatible with magnetic resonance. In all cases, a 3 mm-slice thickness 4D- CT scan with the aid of an abdominal thermoplastic mask was used. 4D-CT scan supports the radiation oncologist to evaluate the heart motion. Cardio-CT scan a 18FDG-PET scan were registered to the average CT simulation scan in order to identify the pathological ventricular area. The target definition was outlined by radiation oncologist and cardiologist. The gross tumor volume (GTV) was delineated as the hypometabolic 18FDG-PET ventricular area. The planning target volume (PTV) was obtained by adding an isotropic margin of 5 mm to the GTV. Dose prescription ranged between 21 and 25 Gy in a single fraction. In all cases were treated with a TrueBeam Linac (Varian Medical Systems, Palo Alto, CA). An approval of the ethics committee was obtained before each radiation treatment. Results From January 2020 to March 2021, 6 RVT patients (5 male and 1 woman) were considered eligible to STAR treatment. The median age was 78 (58-80 years) and median performance status was 2 (range 0-4). Median GTV and PTV volumes were 33 cc (range 10.4-73.3 cc), and 90.8 cc (range 45.9 – 190.1 cc), respectively. Median prescription dose was 25 Gy (range 21- 25 Gy). At a median follow-up of 13 months, an efficacy of STAR treatment was observed in 4 patients. Cardiologist did not record additional defibrillator activation. One patient had RVT recurrence after 3 months by the end of radiotherapy and one patient died due to cardiac failure. No severe acute toxicity was recorded after radiation therapy.