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

Purpose/Objective(s) 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. Materials/Methods 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). Results 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. Conclusion 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.