Conformal Radiotherapy in Patients with Cardiovascular Implantable Electronic Devices: Proposed Practical Implementation of the TG-203 Risk-Stratified Interrogation Schedule

Abstract Introduction Radiotherapy (RT) in patients with cardiac implantable electronic devices (CIED) carries a risk of device malfunction from radiation exposure. We sought to evaluate the incidence of CIED malfunction in a cohort of patients treated with modern RT techniques. Material and Methods A retrospective analysis of 193 CIED patients treated with RT between 2000 and 2018 was conducted. All patients underwent pre-, intra- and post-RT CIED interrogations. Patient demographics, CIED details, RT details including total dose, modality, treatment site, CIED distance from RT field, treatment planning system (TPS) maximum dose and in-vivo dose estimates, and CIED malfunction data were analyzed. Results CIEDs in use were mainly pacemakers (single-chamber 10%, dual-chamber 49%) and defibrillators (35%). Patients received a median RT dose of 50 Gy (range 7-80 Gy), treated with 3DCRT (47%), IMRT/VMAT (38%) and SBRT (10%). Neutron producing energies were used in 13% treatments. A strong correlation was noted between TPS estimated maximum dose and in-vivo estimated CIED dose when the CIED distance from the treatment field was >3 cm. However, in-vivo measurements provide a lower estimated absorbed dose for CIED devices Over a median follow up of 24 months (range 7-64 months), two adverse CIED-related events were recorded: a spontaneous defibrillator discharge and a pacemaker malfunction subsequently causing ventricular tachycardia. Both patients received SBRT to the thorax, with CIED dose of 5 and 19.2 cGy, respectively. Both events occurred two years post-treatment without any intra- or post-RT CIED interrogations changes noted. Conclusions In this series of patients treated with modern RT techniques, we observed a CIED malfunction rate of 1.04%. These low event rates establish the safety of delivering modern RT in CIED patients with the possibility of reducing the burden of intra-/post-treatment CIED monitoring.