A retrospective analysis found 7 percent of patients with cardiovascular implantable electronic devices (CIEDs) had a malfunction attributed to radiotherapy. All of the cases occurred during neuron-producing radiotherapy, prompting lead researcher Jonathan D. Grant, MD, to recommend the use of non-neutron-producing radiotherapy when clinically feasible.
Grant and his colleagues at the University of Texas MD Anderson Cancer Center in Houston published their findings online in JAMA Oncology on June 25.
They noted that guidelines suggest radiotherapy doses of at least 2 Gy were the threshold for clinical concern in patients with cardiac pacemakers or implantable cardioverter-defibrillators (ICDs).
The researchers collected CIED malfunction data from clinical notes, CIED interrogation records, CIED manufacturers and outside cardiologists. They also evaluated the long-term function of CIEDs following radiotherapy.
They examined all patients with CIEDs who underwent radiotherapy at University of Texas MD Anderson Cancer Center between August 2005 and January 2014. In the 215 patients, they identified 249 courses of photon- and electron-based radiotherapy.
Of the patients, 57 percent had pacemakers and 43 percent had ICDs. Further, 23 patients underwent two courses of radiotherapy, four received three courses and one received four courses. The radiologists delivered external-beam photon-only therapy in 203 treatment plans, while 22 plans used a combination of photons and electrons and 10 plans used GammaKnife.
Grant et al identified CIED malfunction in 18 courses of treatment. They found single-event upsets in 15 CIEDs, while two CIEDs underwent two parameter resets and one CIED had nine episodes of data loss.
“The contemporary CIEDs in our series tolerated a consistent range of incident (radiotherapy) doses up to 5.4 Gy with no increase in malfunction risk,” they wrote. “Given the associated expense and potential morbidity, it may be safe to decrease the number of relocation procedures performed.”