Establishing protocols and standards for cardiac radioablation: a path toward clinical integration
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Ventricular tachycardia (VT) and other cardiac arrhythmias are treated with antiarrhythmic drugs, catheter ablation, implantable cardioverter defibrillators, or surgical intervention. In cases where such treatments are ineffective or contra-indicated, these conditions can become life-threatening. Cardiac radioablation, specifically stereotactic ablative body radiotherapy (SABR), offers a promising noninvasive alternative for treating refractory VT. After the first case report from Stanford University, a case series presentation at Washington University in St. Louis contributed to its global expansion [1,2].
A recent paper by Kim et al. [3] outlines an institutional workflow for VT-SABR, emphasizing its technical aspects, treatment planning, and quality assurance (QA) measures. This paper presents two example cases in which advanced multimodal imaging techniques, including electrocardiographic-gated computed tomography (CT), 4-dimensional cone-beam CT (CBCT), and intrafractional CBCT were employed. Despite current capabilities, challenges persist in meeting planned target volume coverage and constraints for specific cardiac substructures, such as the left coronary artery and adjacent structures, illustrating the complexity of balancing therapeutic efficacy against safety. As shown in this study, clearly defining an institutional protocol is crucial as it enables consistent treatment delivery and facilitates standardized reporting of clinical outcomes.
Achieving dose constraints for organs at risk (OARs), including critical cardiac substructures, remains a significant challenge in cardiac radioablation [4]. While insufficient clinical data currently exist to determine the actual incidence of expected toxicities, existing studies have not reported a substantial decline in left ventricular function or a significant increase in coronary artery events after cardiac radioablation [5,6]. To date, long-term effects on myocardial tissue and surrounding OARs remain insufficiently studied, underscoring the need for prospective randomized controlled trials (RCTs) to assess therapeutic efficacy and potential late toxicities. As this treatment is introduced among a high-risk patient population, its integration into standard care requires rigorous procedural frameworks and robust clinical evidence. Concerns among cardiologists remain considerable, emphasizing the importance of interdisciplinary collaboration. In a survey conducted by the European Heart Rhythm Association, 48.1% of respondent cardiologists reported having either performed cardiac radioablation or referred patients for the procedure. Although many acknowledged the potential indications for VT/ventricular fibrillation in patients with underlying structural heart disease, 63% of respondents cited the perceived lack of reliable outcome data as a significant concern [7].
The distinct clinical characteristics of cardiac and oncology patients must be considered when defining and interpreting study endpoints. Researchers in this field must develop a comprehensive understanding of the disciplines involved to foster effective collaboration and ensure meaningful clinical outcomes.
A United States RCT (NCT05765175) aims to address several of these concerns. This study will evaluate the efficacy of cardiac radioablation in reducing arrhythmia burden, assess safety profiles, particularly regarding radiation-induced cardiotoxicity and collateral damage to adjacent organs, and establish benchmarks for imaging, dose delivery, and QA standards applicable across diverse clinical settings [8]. The results of this trial will be instrumental in shaping clinical guidelines and determining whether cardiac radioablation can transition from an experimental procedure to a standard treatment option.
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Conflict of Interest
No potential conflict of interest relevant to this article was reported.