# Radiotherapy with a pacemaker or implanted defibrillator

Source: https://onco.cc/protocols/radiotherapy-with-pacemaker-or-defibrillator/  
OnCo record `radiotherapy-with-pacemaker-or-defibrillator` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Radiotherapy can occasionally upset a pacemaker or an implanted defibrillator, usually by resetting it. Tell the team about your device at your first appointment. They will contact your heart device clinic, plan the treatment to keep dose to the device low, and may watch your heart rhythm during treatment. Your device is checked within two weeks of finishing.

## Summary

The UK Radiotherapy Board guidance (January 2025, with the British Cardio-Oncology Society and the British Heart Rhythm Society) and the JASTRO/JCS guideline (2021) take the same approach: identify the device at referral, obtain the last device check and pacing dependency from the device clinic, consent the patient to the risk of malfunction, and stratify risk by pacing dependency, cumulative device dose and neutron production. Risk of malfunction rises with neutron-producing beams (photons of 10 MV or more, electrons of 20 MeV or more, protons and heavy ions), with high dose rates (flattening-filter-free beams) and with cumulative dose. A meta-analysis of 17 retrospective studies (2,454 patients) found ICDs more often affected than pacemakers (odds ratio 2.75) and reset more likely with neutron-producing radiotherapy.

UK planning rules: energies below 10 MV where possible (otherwise high risk), no direct irradiation of the device including exit beam, the device outlined with a margin (CIED PRV) when within 10 cm of a field edge, and a near-maximum dose (D0.035cc) to the CIED PRV below 5 Gy; a device more than 10 cm from the field edge can be assumed to receive under 2 Gy. Cumulative dose includes previous radiotherapy and cone-beam CT (about 0.01 Gy per scan). Relocating the device is not recommended below 5 Gy. A defibrillator, an AED able to pace and trained staff must be available; continuous ECG monitoring is strongly recommended for pacing-dependent patients, a device nearing end of battery life and ICDs, with an extra trained person on the first day. The device is interrogated weekly once it has received more than 5 Gy and checked within 2 weeks of the course. JASTRO/JCS classify high risk as any of: photons of 10 MV or more, electrons of 20 MeV or more, protons or carbon ions, pacing dependency, device dose above 10 Gy, previous ventricular fibrillation or ICD therapy; low risk needs all of: lower energies, not pacing dependent, no chest irradiation, device dose below 2 Gy and no ventricular tachycardia. None of this is graded; the evidence is case series and laboratory studies.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: CIED and radiotherapy; pacemaker and radiotherapy; ICD and radiotherapy; cardiac implantable electronic device radiotherapy; TG-203; defibrillator radiotherapy; pacing-dependent radiotherapy

## Connected records

- protocols: [MRI safety screening for implants, devices and medicine patches](https://onco.cc/protocols/mri-safety-screening-implants/), [Patient identification and pre-treatment time-out in radiotherapy](https://onco.cc/protocols/radiotherapy-patient-identification-and-time-out/)
- technologies: [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight)](https://onco.cc/technologies/in-room-imaging-systems/)
- terms: [Radiotherapy](https://onco.cc/terms/radiotherapy/)

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