Purpose: To determine whether Proton Beam Therapy (PBT) is associated with less radiation dose than Intensity-Modulated Radiation Therapy (IMRT) to cardiac implantable electronic devices (CIEDs).
Methods: We investigated retrospectively the radiation dose to the CIEDs for 33 patients underwent PBT at our institution between 2010-2020, with targets located close to the CIED, including thoracic, H&N, and esophagus. For each patient, quantitative comparison of dose to the CIEDs between PBT and IMRT was performed.
Results: The CIED distance from edge of field (50% isodose line) ranged 1.5 cm to 22 cm for PBTs. However, due to spread out of dose in IMRTs, edge of fields was closer to the CIEDs, where the distances ranged 1.4 cm to 18 cm. Our results indicate that CIED dose for both PBT and IMRT of all 33 patients were <2Gy, except one patient that IMRT exceed 2 Gy. For this case, IMRT was delivered as initial plan in first 5 fractions, then switched to PBT. We found that the CIED dose in PBT is negligible compare to IMRT. For PBTs of 33 patients, max and mean doses to the CIED were 52.6 and 4.2 cGy, respectively. However, IMRT delivered overall greater dose to the CIED, in which max and mean doses were 216.9 and 73.4 cGy, respectively.
Conclusion: Our study revealed that the clinical treatments with PBT delivered lower dose to the CIEDs (with potentially less induced malfunctions) than those with IMRT. Regardless of treatment modality, the CIED dose depends directly on the distance of the device to the radiation field. However, in PBT, field arrangement is crucial for avoiding irradiation of the device with the distal edge of the Bragg-Peak.