Paroxysmal Atrial Fibrillation in Elderly: Worldwide Preliminary Data of Linac-Based Stereotactic Arrhythmia Radioablation Prospective Phase II Trial

Abstract

<h3>Purpose/Objective(s)</h3> In elderly, paroxysmal Atrial Fibrillation (AF) is difficult to treat with drugs, or by Catheter ablation, so a non-invasive approach should be favorite. No data are published about the use or radiosurgery for AF, thus in the present analysis the preliminary data of a prospective phase-II trial Linac-based STereotectic Arrythmias Radioablation (STAR) for elderly affected by paroxysmal AF were reported. <h3>Materials/Methods</h3> Inclusion criteria were: age ≥70 years; symptomatic paroxysmal AF; intolerance or non-response to anti-arhythmic therapy (AAT). All patients performed 1-week ECG-Holter monitoring, a complete transthoracic echocardiogram before and after STAR. Patients were immobilized using a vac-lock bag and Computed Tomography (CT, 1mm slice-thickness), in the supine position were performed: CT with/without contrast; 4-Dimension CT. STAR was performed in free-breathing with a PTV prescription total dose (Dp) of 25Gy/1 fraction. Flattening Filter Free (FFF), Volumetric Modulated Arc Therapy (VMAT) plan was generated, normalizing 100% Dp to 95% of the volume, while large intra-target dose heterogeneity D2% (PTV)<150%Dp was accepted. The treatment was optimized and delivered by medical linear accelerators (technology company). Image-guided radiotherapy with Cone Beam CT and Surface-Guided RadioTherapy with Align-RT were used to reduce set-up error and to monitor patients during fraction. The primary endpoint is the 1-month post-STAR safety, as complete STAR delivery and no acute treatment-related adverse events more than G3, assessed according to the Common Terminology Criteria for Adverse Events (version 5.0). <h3>Results</h3> From May 2021 to February 2022, 11 patients were treated and followed. In all cases, AAT was stopped at 1 month after treatment. For primary endpoint, no acute treatment-related adverse events were registered (>G1). Only 1 patient experienced G1 esophagitis (7 days from STAR), improved by 5 days of medical therapy. The treatment plan was delivered with 3 no coplanar arcs, in all cases. The mean Overall Treatment Time (OTT) was 3 minutes. For all treated patients with a mean follow-up of 4 months (patients 1-6), no late side effects were reported, and at 3 months, a rare atrial ectopy was documented without AF recurrences. No patients started AAT after radiotherapy. <h3>Conclusion</h3> The present collected data are promising, showing the safety of LINAC-based STAR for AF for the first 11 patients worldwide. This new ablation approach could represent a valid non-invasive alternative for elderly who were excluded from catheter ablation. This trial is registered at ClinicalTrials.gov, NCT04575662.