Dosimetric long-term safety analysis of stereotactic arrhythmia radiotherapy for refractory ventricular tachycardia

Stereotactic arrhythmia radiotherapy (STAR) is a promising treatment for therapy-refractory ventricular tachycardia (VT), and is associated with a substantial reduction in VT burden with only modest short-term toxicity. However, detailed organ-of-interest dosimetry and long-term safety data remain scarce.

To study the association between dosimetry and safety after STAR, we conducted a two-centre, two-platform study on dose to (extra)cardiac organs-of-interest. Patients with therapy-refractory VT were treated with a single fraction of 20-25 Gy and underwent follow-up according to local protocol. Treatment-related adverse events (AEs) were assessed and differences in dose between patients with and without severe AEs were compared.

Twenty-six patients were included (median age 67 years (range 47-83), 88% male, 50% nonischaemic cardiomyopathy). During a median follow-up of 36 months (7-60), seven patients died, two underwent heart transplantation, and two underwent redo-STAR. Six treatment-related severe AEs were observed, all of which were manageable. The mean heart dose was significantly higher in patients with (n = 2) compared to patients without severe pericardial effusion (10.3 and 11.2 vs 6.1 (2.8-13.4) Gy, P = 0.025).

During long-term follow-up, six manageable treatment-related severe AEs were observed, while no treatment-related deaths occurred. Although no STAR-specific dose guidance could yet be defined, routine echocardiographic follow-up focused at valvular dysfunction and pericardial effusion are recommended. Larger, prospective studies are needed to further define the long-term safety profile of STAR and to develop evidence-based dose guidance and follow-up recommendations.