Can Patients Use Continuous Glucose Monitors During Radiation Therapy for Cancer?
By John Hillson, RN, BSN, OCN®
Sally is a 65-year-old patient with T3N1M0 human papillomavirus–negative cancer of the supraglottic larynx who is beginning treatment with radiation and chemotherapy. She has a history of type 1 diabetes mellitus, diabetic retinopathy, diabetic nephropathy, and hospital admissions for diabetic ketoacidosis. She has been using a continuous glucose monitor (CGM) and insulin pump (IP) to help her effectively manage her diabetes. She is concerned that her chemotherapy regimen will involve taking dexamethasone, which will affect her hard-to-control diabetes. Sally tells you she wants to wear her CGM and IP during treatment.
What Would You Do?
You ask the dietician to meet with her and connect Sally’s endocrinologist with the cancer care team. As her nurse, you look up the most recent evidence and information about using CGMs and IPs when undergoing cancer treatment.
The U.S. Food and Drug Administration reported (https://www.fda.gov/radiation-emitting-products/electromagnetic-compatibility-emc/interference-between-ct-and-electronic-medical-devices) a small number of adverse events during computed tomography (CT) imaging of patients wearing IPs and CGMs. One small study of IPs and radiation also reported (https://doi.org/10.1177/1932296818796481) two device malfunctions. A manufacturer-sponsored study looked (https://doi.org/10.1177/1932296820920948) at CGMs exposed to simulated radiation therapy and magnetic resonance imaging (MRI) and found that the devices were functionally intact after ex vivo exposure, although the manufacturer’s website not wearing their device around an MRI or CT scan.
Another manufacturer suggested that patients remove their CGM prior to obtaining x-rays, CT scans, or other types of radiation and avoid use the devices around a strong magnetic field. Still another recommended (https://www.freestyle.abbott/us-en/safety-information.html) removing the device before obtaining x-rays and that exposing the monitor to radiation can cause unreliable low results. However, x-rays and CT scans involve (https://www.radiologyinfo.org/en/info/safety-xray#f36e4a9abeec49a3b973c6bd21bf0b17) far less radiation exposure (https://www.iaea.org/resources/rpop/patients-and-public/radiotherapy) than a single radiation therapy treatment with photons.
Radiation therapy has long been known to be potentially damaging to electronic devices, with the most evidence (https://doi.org/10.1016/j.ijrobp.2018.05.071) surrounding cardiac implanted electronic devices (CIEDs), where ionizing radiation and electromagnetic stimulation have been shown to cause a wide range of effects. Implanted defibrillators and pacemakers can be inappropriately inhibited or prematurely stimulated. Their programming can be altered, data can be corrupted or lost, and they may even completely fail. However, there can also be no apparent damage. Damage to CIEDs is dose dependent (https://doi.org/10.1016/j.radonc.2019.12.007), so common recommendations suggest (https://doi.org/10.1016/j.adro.2021.100732) using shielding or optimizing radiation therapy planning to keep the dose as low as reasonably achievable.
Radiation has been documented (https://ascopubs.org/doi/10.1200/JOP.2012.000717) to damage continuous infusion pumps and intrathecal pumps, although other researchers found (https://doi.org/10.1111/ner.13372) no evidence that intrathecal pumps were harmed. An IV pump manufacturer recommended (https://www.bd.com/documents/guides/user-guides/IF_Alaris-System-8015-v9-19_UG_EN.pdf) avoiding using it near a linear accelerator, but elastomeric pumps have no electronic components and would be expected to remain functional.
Even without irradiation, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recommended (https://www.niddk.nih.gov/health-information/diabetes/overview/managing-diabetes/continuous-glucose-monitoring) that patients perform a finger stick test twice daily to validate their CGM and to not use the device to adjust their insulin doses. NIDDK advised that users change CGMs every three to seven days, based on manufacturers recommendations, but several devices (https://pro.aace.com/cgm/toolkit/cgm-device-comparison) on the market last longer, according to the manufacturers.
You tell Sally that her device’s manufacturer recommends that it not be exposed to radiation, but she elects to wear it anyway. Lacking guidance from the literature, you discuss safe practices with Sally, like paying attention to how she feels and not ignoring symptoms of hypo- or hyperglycemia, even if her CGM monitor reads otherwise. You advise her to do finger stick tests twice daily and to report any discrepancies between her CGM and her conventional glucose monitor and to not place her CGM and insulin pump near the treatment field or anywhere that could be exposed to radiation.