Abstract
Purpose
We describe a case in which a breast cancer patient with an implantable cardioverter-defibrillator (ICD) was treated with postmastectomy followed by axillary radiotherapy. The ICD was partly within the target volume and according to the treatment planning system would receive a maximum dose of about 36 Gy.
Methods and Materials
Postoperatively, the patient had a wound infection needing surgical intervention and 3 months of antibiotics. Therefore, it was decided not to relocate the ICD but instead to switch off the shock function of the ICD for the entire radiotherapy course.
Results
The ICD was successfully substituted with a wearable cardioverter defibrillator (WCD) which the patient wore during the 3-week radiotherapy period until two weeks after the end of treatment. The ICD function was monitored from the start of the treatment until 6 months after treatment.
Conclusions
In situations where an ICD needs to be switched off semi-permanently, a WCD can be used as alternative. The patient in this report tolerated the WCD well. Despite the high dose received by the ICD, the device and its battery continued to function normally.
Introduction
A 67-year aged female presented with left-sided multifocal breast cancer clinical stage I (cT1cmN0, invasive carcinoma NST, histologic grade 1, estrogen and progesterone receptor positive, HER2 negative). She underwent mastectomy, a sentinel node procedure and direct implant-based reconstruction with a tissue expander. Pathological stage was IIB (pT2mN1a(sn) (histologic grade 2, estrogen and progesterone receptor positive, HER2 negative), and she was referred for postoperative radiotherapy. Post-mastectomy radiotherapy was delivered to the chest wall and axillary levels I-III including the supraclavicular lymph node region with three partial 6 MV VMAT arcs (Varian Truebeam) in free breathing. The prescription dose was 4005 cGy in 15 fractions of 267 cGy directed to the left-sided chest wall and axillary lymph nodes levels I-III including the supraclavicular lymph nodes.
The patient had an implantable cardioverter-defibrillator (ICD) (Boston Scientific Pulse generator: Autogen EL ICD D174/ RV shock lead: 0692-59 cm Reliance 4-Front) located in the left chest wall. The ICD was implanted in the context of primary prevention for sudden cardiac death. Since it was partly located within the radiotherapy target volume at least part of it would receive a dose of more than 36 Gy (minimum dose: 3.6 Gy; mean dose: 10.9 Gy; maximum dose: 36.1 Gy). This is much higher than the generally accepted maximum (point) dose of 2 Gy1, 2.
An alternative solution to prevent sudden cardiac death in patients is the temporary use a wearable cardioverter defibrillator (WCD) (i.e., an external ICD). WCDs are typically used in patients:
- •with a high risk for sudden cardiac death, and do not meet the ICD criteria yet;
- •waiting for ICD re-implantation after device infection;
- •who have a reversible cause for their risk of sudden cardiac death but are not (yet) eligible for an implantable defibrillator.
This alternative was identified as the preferred solution in this case and the patient was fitted with a WCD (WCD 4000, Zoll LifeVest) which functioned instead of the implanted ICD throughout the whole period with radiotherapy treatment.
Methods and results
As described in national and international guidelines and reports2, there are several options to reduce the dose to an ICD pulse generator, including relocation. In this patient, relocation away from the treatment fields by means of an operation was not an option due to the complicated postoperative wound infection (Common Toxicity Criteria Adverse events grade 3, version 5.0). The patient also refused any new operation. The dose to the device could not be reduced sufficiently by displacing it laterally with tape away from the high dose regions.
To prevent inappropriate shocks due to electromagnetic interference, it is recommended to place a magnet on top of the pulse generator to temporarily switch off the ICD therapy during each treatment session. In this particular case, due to the location of the ICD in the target volume, placement of the external magnet would block part of the target and could lead to undesirable dose inhomogeneity, varying from day to day. Placement of the magnet during the CT-scan would lead to image distortion which possibly could lead to difficulties with the accurate delineation of the tumor. Because of underdosing the target volume no margin was applied in the treatment planning process to take day-to-day motion of the pulse generator into account within the patient.
Subsequently, the shock function of the implanted ICD was switched off and the device was programmed in a monitor-only setting during the whole treatment period of three weeks. Its functionality was monitored with a remote monitor with alert checks on a daily basis and a full data report on a weekly basis. The patient wore the WCD continuously throughout the whole treatment period except when showering, which was done under surveillance by a family member who had access to an automated external defibrillator (AED) in the patient's residence. During the radiotherapy sessions the WCD was removed, but all sessions were performed under the close supervision of two nurses from the Cardiology Unit, who had direct access to an AED.
The WCD was well tolerated by the patient. After the last treatment the ICD was switched on again and its functioning was verified. No malfunction was detected. For two weeks after treatment the patient wore the WCD as a back-up. The ICD was checked remotely with alert checks on a daily basis and a full data report on a weekly basis until 2 months after treatment completion and thereafter on a monthly basis up to 6 months3. Parameters which were included in these device checks existed of: 1. Lead measurement (impedance, threshold and amplitude); 2. Battery status (voltage and charge time); 3. Diagnostic storage (episodes, measurement trend, histogram; 4. Alert status.
All checks were satisfactory run through and the device did not have to be replaced. In addition, the ICD was observed to function effectively when the patient suffered from multiple episodes of ventricular arrhythmias. More than 6 months after treatment completion the ICD is still functioning properly, the battery status is appropriate and its lifetime is still expected to be around 10 years.
Summary and conclusions
A left-sided breast cancer patient with an ICD located in the left chest wall was treated with post-mastectomy chest wall and axillary radiotherapy. The ICD partly overlapped with the radiotherapy target volume and therefore it would receive a much higher dose than recommended. Device relocation was not wanted by the patient due to the post-operative infection. As an alternative, a WCD was used during the treatment period. This was well accepted by the patient. Periodic checks of the device were performed remotely. Despite the fact that the ICD received a dose of more than 36 Gy no malfunction has been observed up to 6 months after treatment completion. This is not completely unexpected since it has been reported before that an ICD still functions properly after a high dose of irradiation has been received on the device.4 However, it is not uncommon that the battery degrades faster over time because the ICD has received a high dose5. A normal life expectancy of this specific single chamber ICD could be estimated to be between 9 and 11 years depending on the current drain on the ICD battery6. In general it is recommended to perform a more intensive follow-up schedule for at least 6 months after completion of radiotherapy2, 5. Hereafter, if the ICD shows a normal device function the routine follow up schedule, generally every six months, can be resumed7.
According to our best knowledge only one other case report in which radiotherapy has been given in combination with a WCD is described8. This other report describes two patients with lung cancer who wore a WCD after temporary removal of their ICD. In our patient, temporary removal was not advised nor desired by the patient due to the risk of infection. Other publications have described the technology9 and clinical experience10 with WCDs in situations not involving radiotherapy.
In conclusion, if an ICD will receive an unacceptable level of radiation, and relocation prior to treatment is not possible, a WCD can be considered as an alternative. A multidisciplinary approach to such cases involving the treating medical team, medical physicist and cardiology team is essential. Trained cardiology staff should be present with an AED and monitoring equipment during radiotherapy when the WCD is removed. Radiotherapy technologists performing the treatment should be adequately informed about such treatments.
References
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- 6Physician's technical manual Boston Scientific Autogen EL D174: Pulsgenerator longevity, page 51 https://www.bostonscientific.com/content/dam/elabeling/crm/359403-005_multi_PTM_en-USA_S.pdf
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- 10Quast AFBE, Van Dijk VF, Wilde AAAM, et al. Outpatient treatment with the wearable cardioverter defibrillator: clinical experience in two Dutch centres. Neth Heart J. 2017; 25: 312-317 https://doi.org/10.1007/s12471-017-0957-4
Funding statement
No funding for all 3 authors
Dating sharing statement
Anonymized patient data is available on request
Declaration of Competing Interest
No conflicts for all 3 authors
Acknowledgments
No acknowledgments
Article info
Publication history
Published online: March 26, 2023
Accepted:
March 15,
2023
Received:
December 19,
2022
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Copyright
© 2023 The Author(s). Published by Elsevier Inc. on behalf of American Society for Radiation Oncology.
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