Radiotherapy of patients with cardiac implantable electronic devices according to the DEGRO/DGK guideline-is the risk of relevant errors overestimated?

Purpose: Ionizing radiation is able to cause severe damage to cardiac implantable electronic devices (CIED). In Germany, the DEGRO/DGK guideline recommends close monitoring of patients with CIEDs undergoing radiotherapy (RT). Nevertheless, especially in the era of intensity-modulated techniques and predominant use of 6 MV photons, errors of CIEDs are rare events. Therefore, we performed daily CIED controls and hypothesized that no relevant device interaction would occur in our cohort.

Methods: From 2014 to 2018, we collected data of 51 patients (62 courses) with daily interrogation (n = 1046) of CIED. The dose to the skin above the CIED was measured by semiconductor or ion chamber dosimetry at least once per RT course. In many cases the dose was also calculated.

Results: The prescribed dose to the planning target volume (PTV) ranged from 7.5 to 78.0 Gy (IQR 27.8-61.0 Gy). The median measured cumulative dose to the skin above the CIED was 0.17 Gy, whereas the median calculated dose was 1.03 Gy. No error occurred in the group with maximum beam energy >10 MeV. Three events without clinical relevance could be recognized in the group with an intensity-modulated technique at 6 MV. None of the three concerned devices were located directly within the PTV.

Conclusion: Errors of CIEDs during RT are rare events. The approach according to the DEGRO/DGK guideline is safe, but also consumes resources. In our cohort it was not compulsory to relocate any CIED. Clinically relevant events are uncommon, so it remains debatable which procedure is necessary. Daily controls could be avoided in some selected cases without compromising patient safety.