Variability and Main Determinants of Planning Target Volume During Cardiac Stereotactic Radioablation for Refractory Ventricular Arrhythmias: A Systematic Review and Pooled Analysis

ABSTRACT Background Cardiac stereotactic arrhythmia radioablation (STAR) has emerged as a promising alternative for patients with refractory ventricular arrhythmias (VAs). However, the absence of recommendations for margin selection may lead to considerable differences in the treatment plan generation between teams. Objectives This systematic review and pooled analysis aimed at determining the inter‐study variability in target volumes as well as the main drivers of the final treated volume during STAR for refractory VAs. Methods MEDLINE and EMBASE databases were searched until January 31, 2025, to identify all studies describing the use of STAR for treating refractory VAs. Treatment volumes were extracted including clinical target volume (CTV), internal target volume (ITV), and planning target volume (PTV). Volume expansion was assessed using PTV/CTV, ITV/CTV and PTV/ITV ratios. Results A total of 1020 references were retrieved, of which 13 studies met the inclusion criteria, representing 126 patients treated with STAR for VAs. In aggregates, the pooled total volume expansion (PTV/CTV ratio) was 2.8 (95% CI: 2.0–3.6, I 2 = 73%), the pooled volume expansion related to treatment delivery uncertainties (PTV/ITV ratio) was 1.9 (95% CI: 1.7–2.2, I 2 = 12%) and the pooled volume expansion related to cardiorespiratory margins (ITV/CTV ratio) was 1.9 (95% CI: 1.4–2.3, I 2 = 36.5%). Conclusion Generation of the treatment volume in STAR for refractory VA is subject to high variability even among expert teams, with a ninefold difference observed between the smallest and largest reported average PTV. Margins related to uncertainties in treatment delivery seem to contribute as much as margins related to cardiorespiratory movement in determining the final treatment volume. PROSPERO registration: CRD42024580242.