Abstract 4364607: Clinical Impact of Proton Beam Radiation on Pacemakers and ICDs: Insights from the RADIATE-CIED Registry

Background: Patients with cardiac implantable electronic devices (CIEDs) undergoing radiation therapy face potential risks of device malfunction. Proton beam therapy (PBT), with its reduced neutron scatter, has emerged as a potentially safer alternative, yet real-world safety data remain scarce. Methods: We conducted a retrospective cohort study of 100 patients with CIEDs (76 pacemakers, 24 ICDs) who underwent PBT from 2016 to 2023 at a quaternary center. Baseline and serial device interrogations were performed before, during, and after treatment to assess lead impedance, capture thresholds, battery function, and arrhythmic events. Patients were stratified by pacemaker dependence and monitored accordingly. Primary outcomes included device malfunction and new-onset arrhythmias during treatment. Secondary outcomes included device parameter changes, one-year arrhythmia incidence, and cardiac-related hospitalizations. Results: No treatment-related deaths or major device failures occurred. Device malfunction was rare (2 pacemaker patients, 2.6%), with no malfunctions in ICD recipients. Transient, non-clinically significant changes in lead impedance and capture thresholds were observed. Arrhythmias during treatment occurred in 26% of pacemaker and 25% of ICD patients, but only 4% developed new arrhythmias. At one year, device-related complications and cardiac outcomes remained comparable across groups. Independent predictors of arrhythmias during treatment included a higher radiation dose per fraction (OR 1.45; p=0.001), a longer treatment duration (OR 1.12; p=0.04), and a higher number of fractions (OR 1.20; p=0.01). Conclusion: Proton beam therapy appears safe in patients with CIEDs, with a low incidence of clinically significant device malfunctions or arrhythmias. These findings support the integration of PBT into routine practice for this population and underscore the importance of structured monitoring protocols and prospective guideline refinement.