Retrospective Review of Patients With Cardiac Implantable Electronic Devices Treated With Spot Scanning Proton Therapy

Abstract

Purpose/Objective(s): There is limited data on the effects of intensity modulated proton therapy (IMPT) on cardiac implantable electronic devices (CIEDs) such as pacemakers or defibrillators. Neutron scatter could affect CIED function and great caution needs to be taken when treating patients (pts) with CIEDs with IMPT. The purpose of this retrospective study was to review our experience treating CIED pts with IMPT. Materials/Methods: We retrospectively reviewed 50 pts age ≥18 years with CIEDs underwent IMPT for esophageal (11), H&N (10), other GI (7), NSCLC (6), prostate (6), brain (3), and breast (2) cancers, 4 pts with sarcomas and 1 pt with metastatic disease to bone between June 2015 and July 2020 at our institution on this IRB approved study. Thirty-seven pts were male and the average age (range) was 74 years (25-91). CIED manufacturers were Medtronic (21), Boston Scientific (15), Abbott (10), Biotronik (3) and Sorin (1). Forty-three pts had pacemakers and 7 had defibrillators. Eight pts were pacemaker dependent. Prior to treating the first CIED pt with IMPT, a multidisciplinary team including radiation oncology, cardiology, anesthesiology and nursing was established to develop guidelines for safe treatment and monitoring before, during and after IMPT. We implemented a risk-based decision tree for monitoring during treatment based on CIED dependence and underlying heart rate. We report with descriptive statistics pt demographics, cancer diagnosis, dose and distance from CIED, and CIED events and outcomes (CIED malfunctions, resets, battery depletion). Results: Thirteen pts had intensive monitoring of their CIED during IMPT and the remaining 37 pts had reduced monitoring. Overall, 619 fractions were analyzed. The median prescribed proton dose (range) of radiation was 50 GyRBE1.1 in 25 fractions (25-75 GyRBE1.1). 46 pts had zero proton dose to the CIED. Those who had dose to the CIED had an average dose of 0.85 GyRBE1.1 (range of 0.03-2.18 GyRBE1.1). The average distance from CIED was 16.4cm (range: 2.4-> 50cm). There were no major CIED events related to the IMPT. There were three pts who had pacemaker programming resets to manufacturer settings, and all three of these pts had Biotronik CIEDs. These three pts had 6, 1 and 3 resets, and their CIED were 4cm, 7cm and 9cm from the 80% isodose line, respectively. No clinical cardiac events were related to these resets, and the CIEDS were reprogrammed to original settings uneventfully. Routine CIED battery depletion occurred in 2 pts, one of whom underwent CIED replacement during treatment. Projected CIED battery longevity decreased by 1-4 yrs in five pts. Conclusion: Treating pts with CIEDs undergoing IMPT seems to be safe as long as pts are carefully monitored. Infrequent CIED resets may occur. Frequent CIED monitoring may be associated with reduced projected CIED battery longevity. Long term outcomes will be reviewed and reported at the meeting.