Non-invasive cardiac radioablation for ventricular tachycardia: A feasibility dosimetric in silico study based on a prospective cohort of patients to compare photon to proton radiotherapy: Results of the Italian CARA-VT study.

BACKGROUND

Stereotactic arrhythmia radioablation (STAR) may represent an alternative to standard catheter ablation (CA) for treatment of refractory ventricular arrhythmias (VA). Most STAR treatments performed to date have used photon radiotherapy. However, protons have advantageous ballistic properties suitable for this application, potentially improving sparing of organs at risk (OARs).

METHODS

ECG-gated CT scans and electroanatomical mapping were performed to reconstruct a 3D bipolar voltage map and identify ablation targets in a cohort of patients with VA candidates for CA. Three radiation treatment modalities were investigated/compared using the breath-hold technique: photon volumetric modulated arc therapy (VMAT) and proton active pencil beam scanning delivered with/without cardiac gating. When cardiac gating was applied, the diastolic phase-longer and more stable than the systolic one-was selected as the reference.

RESULTS

Twenty-three patients were enrolled, and three presented multifocal ventricular arrhythmias, resulting in a total of 27 treatment targets. Both photon and proton plans achieved adequate target coverage. Compared with photon plans, proton therapy showed a statistically significant reduction in the mean maximum dose to several OARs and to important non-target cardiac structures (coronary arteries, valvular apparatus and right atrium) while maintaining comparable target coverage. These findings were consistent for proton plans with and without cardiac gating. In a subset of 14 patients, cardiac gating provided additional reductions in dose to healthy cardiac tissue.

CONCLUSIONS

This in-silico study suggests that STAR using proton beams may significantly reduce radiation exposure to non-target cardiac substructures and surrounding extracardiac OARs, regardless of the cardiac motion management strategy adopted.