Interdisciplinary clinical target volume generation for cardiac radioablation: Multi-center benchmarking for the RAdiosurgery for VENtricular TAchycardia (RAVENTA) trial.

Abstract Background Cardiac radioablation is a novel treatment option for therapy-refractory ventricular tachycardia (VT) ineligible for catheter-ablation. Three-dimensional clinical target volume (CTV) definition is a key step and this complex interdisciplinary procedure includes VT-substrate identification based on electroanatomical mapping (EAM) and its transfer to the planning-CT (PCT). Benchmarking of this process is necessary for multi-center clinical studies such as the XXX trial. Methods For benchmarking of the XXX-trial, patient data (epicrisis, ECG, high-resolution EAM, contrast-enhanced cardiac-CT, PCT) of three cases were sent to five university centers for independent CTV -generation, subsequent structure analysis and consensus finding. VT-substrates were first defined on multiple EAM screenshots/videos and manually transferred to the PCT. The generated structure characteristics were then independently analyzed (volume, localization, surface distance and conformity). After subsequent discussion, consensus structures were defined. Results VT-substrate on the EAM showed visible variability in extent and localization for cases 1 and 2 and only minor variability for case 3. CTVs ranged between 6.7-22.9cm3, 5.9-79.9cm3 and 9.4-34.3cm3; surface area varied between 1087-3285mm2, 1077-9500mm2 and 1620-4179mm2, with a Hausdorff-distance between 15.7-39.5mm, 23.1-43.5mm and 15.9–43.9mm for case 1-3, respectively. The absolute 3D-center-of-mass difference was 5.8-28.0mm, 8.4-26mm and 3.8-35.1mm for case 1-3, respectively. The entire process resulted in CTV-structures with a conformity-index between 0.2-0.83, 0.02–0.85 and 0.02–0.88 (ideal 1) with the consensus-CTV as reference. Conclusions Multi-center efficacy endpoint assessment of cardiac radioablation for therapy-refractory VT requires consistent CTV-transfer methods from the EAM to the PCT. VT-substrate definition and CTVs were comparable with current clinical practice. Remarkable differences regarding the degree of agreement of the CTV-definition on the EAM and on the PCT were noted, indicating a loss of agreement during the transfer process between EAM and PCT. Cardiac radioablation should be performed under well-defined protocols and in clinical trials with benchmarking and consensus forming.