Conformal Radiation Therapy in Patients With Cardiovascular Implantable Electronic Devices: Proposed Practical Implementation of the 2019 American Association of Physicists in Medicine Task Group No. 203 Risk-Stratified Interrogation Schedule.

Abstract

Radiation therapy (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. 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 maximum dose and in vivo dose estimates, and CIED malfunction data were analyzed. 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 3-dimensional CRT (47%), intensity modulated RT/volumetric modulated arc therapy (38%), and stereotactic body radiation therapy (10%). Neutron producing energies were used in 13% of the treatments. A strong correlation was noted between treatment planning system 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 <3 cm from the RT field. During a median follow-up of 24 months (range, 7-64 months), 2 adverse CIED-related events were recorded: a spontaneous defibrillator discharge and a pacemaker malfunction subsequently causing ventricular tachycardia. Both patients received stereotactic body radiation therapy to the thorax, with CIED dose of 5 and 19.2 cGy, respectively. Both events occurred 2 years posttreatment without any intra- or post-RT CIED interrogations changes noted. 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- and posttreatment CIED monitoring.