Implantable Devices May Fail During Cancer Radiotherapy

Patients with cardiac implantable electronic devices (CIEDs) may be at increased risk of device malfunction when undergoing radiotherapy (RT) for cancer, according to a new study.

Researchers at the University of Texas MD Anderson Cancer Center (Houston, USA) conducted a retrospective analysis of all patients with a functioning CIED who underwent RT between August 2005 and January 2014. They identified 249 courses of RT in 215 patients (57% with pacemakers and 43% with implantable cardioverter defibrillators (ICDs)). The main outcomes and measures were CIED malfunction, characterized as single-event upsets—data loss, parameter resets, unrecoverable resets—and delayed effects, including signal interference, pacing threshold changes, and premature battery depletion.

The results showed that malfunction of CIED attributable to RT occurred during 18 courses (7%), with 15 CIEDs experiencing single-event upsets, and three transient signal interference cases, for a total device compromise rate of 21%. All single-event upsets occurred during neutron-producing RT; no single-event upsets were found among 178 courses of non-neutron-producing RT. Patients treated to the abdomen and pelvis region were more likely to undergo a single-event upset. No delayed malfunctions were directly attributed to RT. The study was published online on June 25, 2015, in JAMA Oncology.

“In the absence of clinical benefit for higher-energy RT, the use of non-neutron-producing RT is recommended to avoid single-event upsets,” concluded lead author Jonathan Grant, MD, and colleagues of the department of radiation oncology. “If higher RT energies provide clinical benefit, however, the error rates and outcomes that we report will aid clinicians in weighing the risks of using neutron-producing RT.”

“Basically, these events represent device compromise due to a change in the memory state of the circuitry,” said Charles Thomas, Jr. MD, PhD, professor and chairman of the department of radiation medicine at Oregon Health and Science University (Portland, OR, USA), in an accompanying editorial. “There exists an opportunity to design trials that incorporate next-generation and commercially available electronic monitoring devices in this patient population to detect more subtle dysrhythmias, device sensor adjustments, and/or transient threshold alterations.”

Single-event upsets in CIEDs caused by high-energy radiation result when high-energy photons (over 10 MV) interact with materials in a linear accelerator, causing high-energy neutrons to be emitted throughout the treatment room. The neutrons interact thermally with boron atoms found in the metal oxide semiconductor components contained in contemporary CIEDs, causing disruptions in the electric currents.

Related Links:
University of Texas MD Anderson Cancer Center