Radiotherapy and implanted cardioverter defibrillators: novel techniques make it feasible

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Ionizing radiation may interfere with electric components of pacemakers or implantable cardioverter defibrillators (ICDs). More recently, a number of studies have reported an increase in radiation sensitivity of these devices (encompassing the coiled metal leads and generator unit) due to the incorporation of complementary metal oxide semiconductor circuitry.1,2 The type, severity and extent of radiation damage to these devices depend on the total dose and rate.
We report the case of a 70-year-old male patient with non-small cell lung cancer presenting as a sub-carinal paraesophageal lesion, detected by 18F-fludeoxyglucose (18FDG) computed tomography (CT)/positron emission tomography (PET), who was referred for radiotherapy in the Department of Radiation Oncology of our Institution. The patient had a history of dilated cardiomyopathy, and an implantable cardioverter defibrillator (ICD) (Medtonic Maximo II VR) had been implanted 3 years ago with subsequent appropriate activation. The decision of a multidisciplinary meeting was to keep the ICD in place and deliver 64 Gy in 32 fractions for controlling the tumour growth using an intensity-modulated radiation therapy (IMRT) technique by means of helical tomotherapy with 6-MV photons. The patient underwent an 18-FDG CT/PET scan to identify the metabolic target treating volume. The helical tomotherapy treatment plan was made in order to spare as much as possible the cardiac device and the organs at risk. The patient received a total dose of 64 Gy in 32 fractions. The radiotherapy was well tolerated without any side effects. Prior to each treatment, a megavoltage CT was performed in order to verify the exact patient positioning. The patient received his first treatment in the presence of a radiation oncologist and a cardiologist while the device was telemetrically monitored during the entire radiotherapy course. Device interrogation was thereafter performed before and after the radiotherapy treatment without indicating any malfunction.
Helical tomotherapy is a new image-guided IMRT technique that provides better dose uniformity, dose gradients, and protection for the lung and organs at risk. The ability of helical tomotherapy to spare critical organs immediately adjacent to the tumour target was very good and the dose to the ICD was less than 5 Gy, thus making helical tomotherapy for these centrally located lesions feasible also in the presence of cardiac devices. The dose to the proximal defibrillator coil supervened 30 Gy uneventfully, although no particular limitations were available (Figs 1 and 2).
The oncologic prognosis must be weighted against the cardiologic prognosis in a multidisciplinary setting. Innovative irradiation techniques and technological sophistications of pacemakers and ICDs have potentially changed the tolerance profiles.1,2 Although updated guidelines are needed with acceptable dose criteria for implantable cardiac devices, it is possible to treat patients with these devices and parts encroaching on the radiation field. This case report shows we were able to safely treat our patients through a multidisciplinary approach, monitoring the patient during each step of the treatment.

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