Safety verification of carbon-ion radiotherapy for patients with cardiac implantable electronic devices (CIEDs)

Abstract

According to guidelines, carbon-ion beam therapy is considered to carry a high safety risk for patients with cardiac implantable electronic devices (CIEDs), although the actual impacts remain unclear. In this study, we investigated the safety of carbon-ion beam therapy in patients with CIEDs. Patients with CIEDs who underwent carbon-ion therapy at Gunma University Heavy Ion Medical Center between June 2010 and December 2019 were identified and investigated for abnormalities in the operation of their CIEDs, such as oversensing and resetting during irradiation, and abnormalities in operation after treatment. In addition, the risk of irradiation from carbon-ion beam therapy was evaluated by model simulations. Twenty patients (22 sites) with CIEDs were identified, 19 with pacemakers and one with an implantable cardioverter-defibrillator (ICD). Treatments were completed without any problems, except for one case in which the treatment was discontinued because of worsening of the primary disease. Monte Carlo simulation indicated that the carbon beam irradiation produced neutrons at a constant and high level in the irradiation field. Nevertheless, with the distances between the CIEDs and the irradiation fields in the analyzed cases, the quantity of neutrons at the CIEDs was lower than that within the irradiation. Although carbon-ion beam therapy can be safely administered to patients with CIEDs, it is advisable to perform the therapy with sufficient preparation and backup devices because of the risks involved.

Keywords: Monte Carlo simulation; carbon-ion; cardiac implantable electronic devices (CIEDs); implantable cardioverter-defibrillator (ICD); pacemaker; radiotherapy.

Fig. 1

Simulation set-up. The green region represents the water phantom simulating the human body. The head part of the phantom was a sphere with a radius of 10 cm, and the body part was rectangular (10 × 21 × 120 cm) with two semicircular columns (radius = 10.5 cm) (B). The beam was irradiated at a 20 cm distance, from the shoulder to the foot side. The blue circles indicate the calculation points for the energy spectra of the neutron flux. The MLC was shaped 10 cm square (C).

Fig. 2

PHITS simulation results. (A) The neutron flux along the medial line: straight line, without the MLC; Dashed line, with the MLC. (B) The 2-dimentional distribution of the neutrons (1) thermal neutrons, (2) epi-thermal neutrons, and (3) fast neutrons.