ESTRO 38 Abstract book

S469 ESTRO 38

Material and Methods Enrolled patients suffered from recurrent VT or electrical storm (ES) refractory to CA and AADs. Before the procedure, an electroanatomic mapping (EAM) was performed to localize the VT substrate (VT-sub). All patients underwent a planning CT co-registered with a cardiac MRI or a cardiac CT to help in volume definition. For each case, the cardiologist delineated the VT-sub according to the EAM data. The distal dipole of the ICD lead was used as a fiducial marker for tracking. The median dose of 25 Gy (range, 20–25 Gy) was delivered to the VT-sub using the Cyberknife ® system. Results Since September 2017, five patients with VT or ES refractory to AADs and CA were treated. Four patients were elective, while another one, hospitalized in the intensive care unit (ICU), was intubated because of an ES with multiple ICD shocks refractory to CA. VT was due to an ischemic cardiomyopathy in two patients and to a non- ischemic cardiomyopathy in the three others. In all patients, SBRT was successfully delivered using near real- time ICD lead tracking with an average time of 54 minutes. The median ablation volume was 22 cc (range, 19-35 cc). After a median follow-up of 5 months (range, 4-11), the elective patients did not experience any VT recurrence. The ICU patient, suffering from a non-ischemic cardiomyopathy, was extubated 3 days after SBRT and remained free of ICD shocks during 4 months; he presented, however, a new ES episode 19 weeks after the procedure related to a new VT-sub successfully treated by CA. In all patients, the ICD interrogation confirmed that no sustained VT episodes arose from the irradiated site after SBRT. Importantly, no SBRT-related toxicity occurred. Conclusion SBRT appears as an efficient tool for the treatment of refractory VT caused by myocardial scarring. Recurrence was observed only in non-ischemic cardiomyopathy remote from the irradiated site. PO-0889 Breathing modulation in patients treated for mobile tumours: moving forward to clinical integration G. Van Ooteghem 1,2 , D. Dasnoy-Sumell 3 , G. Liistro 4 , E. Sterpin 5 , G. Xavier 1,2 1 Institut de Recherche Expérimentale et Clinique, Molecular Imaging- Radiotherapy and Oncology MIRO, Brussels, Belgium ; 2 Cliniques Universitaires Saint Luc, Radiation Oncology, Brussels, Belgium ; 3 Université Catholique de Louvain, ImagX-R, Louvain-La-Neuve, Belgium ; 4 Cliniques Universitaires Saint Luc, Pneumology, Brussels, Belgium ; 5 Université Catholique de Louvain, Molecular Imaging- Radiotherapy and Oncology MIRO, Brussels, Belgium Purpose or Objective We previously demonstrated that mechanically-assisted and non-invasive ventilation (MANIV) can be used safely without sedation on healthy volunteers. MANIV can be used to regularise the breathing pattern by constraining the breathing rate (BR) and the tidal volume (Volume- controlled ventilation mode – VC). Breathing modulation can also be achieved by the shallow-controlled mode (SH) which reduces the breathing amplitude proportionally to the BR increase while the Slow-controlled mode (SL) mimics repeated end-inspiratory breath-holds. To allow the clinical integration of MANIV in radiotherapy, patients’ tolerance and the intra- and inter-session reproducibility of the breathing-related tumour motion were thus evaluated. Material and Methods In lung or liver cancer patients (cohort A), the tumour motion was assessed with the VC and SH modes and compared to spontaneous breathing (SP). In left breast cancer patients (cohort B), the nipple motion was assessed with the SL mode and compared to spontaneous breath-

PO-0888 Stereotactic body radiotherapy for refractory ventricular tachycardia: clinical outcomes R. Jumeau 1 , M. Ozsahin 1 , J. Schwitter 2 , F. Duclos 1 , V. Vallet 3 , M. Zeverino 3 , R. Moeckli 3 , E. Pruvot 4 , J. Bourhis 1 1 Centre Hospitalier Universitaire Vaudois, Department of Radiation Oncology, Lausanne Vaud, Switzerland ; 2 Centre Hospitalier Universitaire Vaudois, Cardiac MR center, Lausanne Vaud, Switzerland ; 3 Centre Hospitalier Universitaire Vaudois, Department of Radiation Physics, Lausanne Vaud, Switzerland ; 4 Centre Hospitalier Universitaire Vaudois, Department of Cardiology, Lausanne Vaud, Switzerland Purpose or Objective Ventricular tachycardia (VT) caused by myocardial scarring bears a significant risk of mortality and morbidity that can be partially controlled by the implantation of a cardioverter-defibrillator (ICD). Recently, stereotactic body radiotherapy (SBRT) appeared as a promising tool for the management of VT refractory to antiarrhythmic drugs (AADs) and catheter ablation (CA). We present herein the outcomes of our series of patients treated under an institutional SBRT program for refractory VT.