Early feasibility study of catheter-free cardiac radioablation with proton beams for refractory ventricular tachycardia.

BACKGROUND

Clinical data supporting cardiac radioablation (CRA) for ventricular tachycardia (VT) are currently limited to photon-based irradiation. Proton irradiation may allow more precise targeting with reduced radiation exposure of non-target tissues.

OBJECTIVE

This study aimed to evaluate the early-stage feasibility of catheter-free proton CRA for the management of refractory VT.

METHODS

This first-in-human, non-randomized trial enrolled patients with left ventricular ejection fraction (LVEF) <50% and VT refractory to antiarrhythmic drugs and prior catheter ablation(s). A single fraction of 30 Gy intensity-modulated proton therapy was delivered. Patients were followed for up to 2 years post-treatment.

RESULTS

7 patients underwent treatment (6 males, mean age 68 years). Median target volume was 17cm3 (range 8.3-64.9 cm3). A median of only 4% of non-target myocardium received ≥20 Gy. Patients were followed for a median of 514 days (range 66-730 days, cumulative 107 patient-months). The rate of VT events declined from 7.24 per patient-month in the 3 months before treatment to 1.52 per patient-month during follow-up (79% event rate reduction). No probable or definite treatment-related serious adverse events occurred. Median LVEF was 26% (IQR 23%-39%) at baseline and 25% (IQR 18%-32%) at last available follow-up. 2 patients underwent heart transplant 66 and 514 days after treatment because of end-stage heart failure and VT, and 3 patients died at 155 days (end-stage heart failure), 502 days (end-stage heart failure), and 529 days (sudden non-arrhythmic death, likely heart failure-related).

CONCLUSION

Catheter-free proton CRA for refractory VT was feasible and without definite evidence of associated toxicity, supporting further investigation in larger prospective studies.