Risk of radiotherapy upsetting implantable heart devices: It’s all about the neutrons

When implantable heart-help devices malfunction in cancer patients undergoing non-neutron-producing radiation therapy (RT), don’t blame the malfunction on the therapy.

However, before administering neutron-producing RT, especially in energy levels exceeding 10 megavolts, radiation oncologists should give careful consideration to the patient’s individual risk-benefit profile.

These conclusions come from a study in which single-event device upsets occurred during neutron-producing RT at rates of 21 percent in cardiovascular implantable electronic devices (CIEDs) and 10 percent in pacemakers.  

By contrast, zero single-event upsets were observed among 178 courses of non-neutron-producing RT.

The study behind the numbers, led by Jonathan Grant, MD, of the University of Texas MD Anderson Cancer Center, ran in JAMA Oncology in June. It posted online Aug. 17, with extrapolation from Zian H. Tseng, MD, a cardiologist and cardiac electrophysiologist at UC-San Francisco, in JAMA Internal Medicine. 

In the study, Grant and colleagues retrospectively analyzed 249 RT courses in 215 patients (123 with pacemakers and 92 with ICDs) over a nine-year period at a single academic medical center.

They recommended that non-neutron-producing RT be used for these patients whenever it will suffice.  

In the new article, Tseng notes that this work builds on previous studies showing that the focus of concern should be on neutron emission with higher beam energies rather than total radiation dose.

“These studies contribute to the modern experience suggesting that RT is generally safe in patients with contemporary CIEDs, and demonstrate that malfunctions are relatively uncommon, nearly always software based, and transient when they do occur,” writes Tseng.

Such malfunctions should be caught by careful monitoring during RT and systematic interrogations before and after therapy, he continues, adding that such monitoring is essential to RT protocols.

Explaining the importance of the research, Tseng points out that case reports in the press of heart devices going haywire “can heighten the anxiety of both radiation oncology and cardiac electrophysiology specialists in the care of patients with CIEDs undergoing RT.”