Ce-452773-1 proton cardiac radioablation for refractory ventricular tachycardia: dose distribution to target myocardium and organs at risk

Cardiac radioablation has emerged as a novel approach for the treatment of refractory scar-related ventricular tachycardia (VT). Current clinical evidence for this approach is limited to photon treatments. Cardiac and extracardiac radiation dose distributions in humans treated for VT with proton beam therapy have not been previously reported. To evaluate radiation dose distributions to target myocardium and to organs-at-risk (OAR) with intensity modulated proton therapy (IMPT). Dose volume histograms were analyzed in 6 patients (5 males; age 67.7±5.2 years) with refractory VT despite antiarrhythmic drugs and catheter ablation who were treated with IMPT in the setting of an ongoing single-center first-in-human clinical trial. In each patient, a single fraction of 30 Gy to target myocardium was prescribed. Among all patients, the median Clinical Target Volume was 17 cc (range 8.3-64.9 cc) and median non-target myocardial volume was 285.5 cc (range 185.1-329 cc). Median maximum voxel dose to target myocardium was 38 Gy (range 35.2-38.9 Gy) while only a median 4.3% (range 3.6-7.9%) of non-target myocardium received ≥20 Gy. Averaged dose distributions to other OARs are shown in the Table. Among extracardiac OARs, the median percentage of total lung volume receiving ≥10Gy was 0.1% (range 0-5.7%). Among coronary arteries, the left anterior descending received max voxel doses ranging from 17.7 to 27.9 Gy without clinical consequences. These first-in-human data of proton beam therapy for refractory VT demonstrate that therapeutic doses can be delivered to target myocardium with low radiation exposure of cardiac and extracardiac OARs.