ESTRO 2022 - Abstract Book

S892

Abstract book

ESTRO 2022

Oncology, Department of Radiotherapy, Gliwice, Poland; 10 Medical University of Gda ń sk, Department of Oncology and Radiotherapy, Gda ń sk, Poland; 11 Medical University of Silesia, First Department of Cardiology, Katowice, Poland Purpose or Objective The SMART-VT trial aims to assess the safety of electrophysiology-guided non-invasive radioablation (STAR) for ventricular tachycardia (VT) in patients with structural heart disease and recurrent, clinically significant VT, despite adequate pharmacotherapy, implantable cardioverter-defibrillator (ICD), and prior catheter ablations. We present the pre-planned interim safety analysis results, including the first seven patients out of the planned 11-patients group and a report on the initial assessment of treatment efficacy. Materials and Methods Seven patients were treated between 12.2020 and 06.2021 with a total dose of 25 Gy in a single fraction which was prescribed to the arrhythmia substrate (Fig. 1). The target volume was defined using invasive electroanatomic mapping and contrast-enhanced cardiac-gated CT. The gross target volume was adjusted for the cardiac movement based on cardiac- gated CT and expanded by a 3-millimeter uniform planning target volume margin. The treatment was performed on Varian EDGE TM linear accelerator using Volumetric Modulated Arc Therapy and Deep-Inspiration Breath Hold technique. The primary endpoint of the study was defined as a 3-month observation without severe (grade ≥ 3) adverse events (AE) in at least 6 out of 7 patients (1st stage), and in total in at least 9 out of 11 patients (2nd stage). Severity of symptoms was assessed according to CTCAE v5.0. The secondary endpoints included reduction of VT burden and ICD treatments, based on the ICD interrogations. Figure 1. Dose distribution

Results The results of the interim analysis demonstrated that the primary endpoint of the first phase of the study has been met. Within the 3-months follow-up period after the treatment, we observed one episode of severe AE potentially associated with treatment. Patient #2 developed clinical grade 3 heart failure exacerbation at 3 months after the treatment, which led to an unplanned hospitalization. The patient remained hospitalized for 11 days, receiving inotropic agents, and right pleural thoracocentesis. The AE subsided with no permanent sequelae. The summary of treatment efficacy is presented in Table 1. Patients #2 and #5 experienced a transient increase in VT burden shortly after STAR. The majority of the patients experienced a significant reduction of VT burden and ICD treatments

after the blanking period. Table 1. Treatment efficacy