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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.
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.
Why: Whether the heart relies on the device decides how serious a malfunction would be.
“It is imperative to identify patients with CIEDs as early as possible within the radiotherapy pathway.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: The team needs to know how the device is set and how the heart behaves before any treatment.
“Ensure the CIED is under regular follow-up and request a report of the last device check and documentation of all programmed parameters”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: The patient should know what could happen and what the team will do about it before agreeing to treatment.
“Ensure an appropriately trained practitioner has had a risk-benefit discussion with the patient regarding possible device malfunction and management during radiotherapy.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: Small or leadless devices are easy to miss, and a short CT scan carries very little risk to the device.
“If a device is more than 10cm from a potential field edge it is not necessary to include in the planning CT scan (radiotherapy dose will be <2Gy).”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: Higher energies make neutrons that can scramble the device's memory; keeping the beam off the device keeps its dose low.
“Use energies <10MV to minimise neutron production. If energies at 10MV and above cannot be avoided, then the patient must be managed within the high-risk category.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: The total dose the device receives over the whole course is what raises the chance of a fault.
“Recommended near-maximum dose (eg. D0.035cc) to CIED PRV is <5Gy.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: Treating the cancer properly comes first, and moving a device is an operation with its own risks.
“The quality of the treatment plan should not be significantly compromised for the sake of sparing the device.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: If the device fails, the team must be able to support the heart at once.
“A cardiac arrest trolley equipped with an automated external defibrillator (AED) capable of delivering external pacing is available within the department and staff are adequately trained to use the equipment.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: Watching the heart rhythm lets staff stop the beam the moment something goes wrong.
“There is a lack of data on the benefit of continuous cardiac monitoring during radiotherapy2, but it is strongly recommended to use cardiac monitoring for patients who are pacing dependent, those whose device battery is nearing end of life or those with ICDs24.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: A magnet pauses the defibrillator's shocks without stopping its pacing, but the shocks may be needed if the rhythm is truly dangerous.
“If an ICD appears to be delivering shocks inappropriately, a magnet positioned over the device will stop the delivery of shocks and anti-tachycardia therapy but will not affect the pacemaker function of the ICD.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: Some faults appear only later, so the device is checked again after treatment ends.
“The patient must have their CIED checked at their referring hospital within 2 weeks of completing treatment.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
Why: Faults are rare, and reporting them is how guidance improves.
“All unexpected CIED events detected during the radiotherapy course and in the follow-up period must be systematically recorded using the centre’s incident reporting system and explained to the patient.”
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Guidance (ungraded)
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
Identify the device at referral, obtain its settings and pacing dependency from the device clinic, consent to the risk, and stratify risk by pacing dependency, cumulative device dose and neutron production (UK Radiotherapy Board 2025; JASTRO/JCS 2021; AAPM TG-203 2019 frames the same process as a failure-mode analysis). Plan below 10 MV with flattened beams, keep the beam off the device and aim for a near-maximum cumulative device dose below 5 Gy (UK), without compromising the cancer plan; monitor pacing-dependent patients, ICDs and devices near end of life by ECG with resuscitation and external pacing to hand; check the device within 2 weeks of the course. The guidelines differ on thresholds: the UK counts any treatment at 10 MV or above as high risk and sets 5 Gy as the dose aim, while JASTRO/JCS calls a device dose above 10 Gy high risk and below 2 Gy (with no chest irradiation) low risk, and raises risk one level for flattening-filter-free beams; Italian AIAC/AIRO/AIFM draws its energy line at 6 MV. None of these is graded, because the evidence is case series and laboratory studies.
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · Japanese Society for Radiation Oncology and Japanese Circulation Society (Journal of Radiation Research) 2021 · American Association of Physicists in Medicine (Miften et al., Medical Physics) 2019 · Heart Rhythm 2023
Where it differs: Low risk requires photons below 10 MV or electrons below 20 MeV, no pacing dependency, no chest irradiation, device dose below 2 Gy and no history of ventricular tachycardia; high risk is any of photons of 10 MV or more, electrons of 20 MeV or more, protons, carbon ions, pacing dependency, device dose above 10 Gy, previous ventricular fibrillation or ICD therapy. Medium-risk patients are monitored by ECG or pulse oximeter at the first session and as needed after; high-risk patients at every session. FFF beams can raise the category by one level.
Evidence: Consensus of the Japanese radiation oncology and cardiology societies, based on case reports and laboratory studies; ungraded.
Where it differs: As tabulated by the UK and JASTRO/JCS documents, the Italian classification counts as low risk only photons or electrons of 6 MV or less with device dose of 2 Gy or less and no pacing dependency, and as high risk a device dose above 10 Gy; the 2025 ANMCO statement adds timing of cardiology assessments during and after treatment.
Evidence: Expert consensus. The ANMCO statement was read as an abstract only.
Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 · ANMCO (Giornale Italiano di Cardiologia) 2025
Where it differs: Use continuous cardiac monitoring where available, keep doses below 2 Gy (departments set rules for a safe distance from field edge to device when dose is not calculated), and refer for a device check within 2 weeks.
Evidence: Pragmatic guidance; ungraded.
| Recommendation | Grade, as printed | Source |
|---|---|---|
| Implantable defibrillators are more often affected by radiotherapy than pacemakers “The meta-analysis showed that RT was associated with an increased risk of ICD malfunctions (odds ratio [OR] 2.75; 95% confidence interval [CI] 1.74-4.33).” | Meta-analysis of 17 retrospective observational studies (2,454 patients) | Heart Rhythm 2023 |
| Neutron-producing radiotherapy raises the risk of device malfunction “Neutron-generating RT significantly increased the risk of CIED malfunctions (OR 3.97; 95% CI 1.70-9.26), especially the risk of reset (OR 5.79; 95% CI 2.37-14.12; P = .0001).” | Meta-analysis of observational studies | Heart Rhythm 2023 |
| Continuous monitoring for high-risk patients at every session “For high-risk patients, monitor the circulation using an electrocardiogram or pulse oximeter for pulse abnormalities in every radiotherapy session.” | Guideline (ungraded) | Japanese Society for Radiation Oncology and Japanese Circulation Society (Journal of Radiation Research) 2021 |
| Flattening-filter-free beams raise the risk category “When using flattening filter-free (FFF) beams, consider raising the risk classification by one level depending on the patient’s condition.” | Guideline (ungraded) | Japanese Society for Radiation Oncology and Japanese Circulation Society (Journal of Radiation Research) 2021 |
| A device more than 10 cm from the field edge can be assumed to receive under 2 Gy “If the CIED is >10cm superiorly or inferiorly from the edge of the treatment beam, it can be assumed that the near-maximum dose (eg. D0.035cc) to the CIED PRV will be <2Gy.” | Guidance (ungraded) | Radiotherapy Board (IPEM, Society and College of Radiographers, Royal College of Radiologists), with the British Cardio-Oncology Society and the British Heart Rhythm Society 2025 |
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Shares In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight), Radiotherapy.
Shares In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight), Radiotherapy, IMRT / IGRT (modern external beam).
Shares Patient identification and pre-treatment time-out in radiotherapy, In-room imaging for radiotherapy (cone-beam CT, ExacTrac, CT-on-rails, HyperSight).