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C A S E R E P O R T Open Access
Pacemaker and radiotherapy in breast cancer: is
targeted intraoperative radiotherapy the answer
in this setting?
Mohammed RS Keshtgar
1*
, David J Eaton
2
, Claire Reynolds
2
, Katharine Pigott
2
, Tim Davidson
1
,
Benjamin Gauter-Fleckenstein
3
and Frederik Wenz
3
Abstract
We present the case of an 83 year old woman with a cardiac pacemaker located close in distance to a
subsequently diagnosed invasive ductal carcinoma of the left breast. Short range intraoperative radiotherapy was
given following wide local excision and sentinel node biopsy. The challenges of using ionising radiation with
pacemakers is also discussed.
Keywords: Pacemaker, Safety, Targeted intraoperative radiotherapy (TARGIT), INTRABEAM, Breast cancer
Background
Ionising radiation (IR) has been reported to interfere
with modern cardiac pacemakers (PM), which are
equipped with complementary metal oxide semicon-
ductor circuitry (CMOS) [1]. In 1994, the American As-
sociation of Physicists in Medicine (AAPM) stated that a
cardiac pacemaker can fail at radiotherapy doses as low
as 10 Gy, and even doses of 2 Gy could lead to signifi-
cant functional changes. This resulted in guidelines sug-
gesting that the dose to the PM should be limited to
2 Gy [2].
The cardiac conditions which lead to the implantation
of a PM are typically sick sinus syndrome, high grade
atrio-ventricular (AV) blockade IIb, type mobitz, or total
AV-blockade III. Patients suffering from high grade AV-
blockade depend highly on external functional cardiac
pacing since cardiac output is directly related to left ven-
tricular pump function and heart rate. Arrhythmia
results in inconstant and insufficient ventricular filling
and decreased ventricular ejection fraction. This, in
combination with a very low heart rate (30–50 bpm),
gives rise to very low cerebral, coronary, intestinal, pul-
monary and renal perfusion pressure, leading to ische-
mia. The patients at highest risk from pacemaker
dysfunction are those who are absolutely dependent on
their PM, who are without a sufficient escape rhythm.
Cardiac pacemakers are programmed to sense brady-
cardia and to pace the heart through implanted metal
coil leads which are not sufficiently shielded against
radiation.
Modern PMs contain CMOS circuitry and random ac-
cess memory (RAM), in addition to the battery and leads
capable of sensing and pacing the heart. The CMOS is cap-
able of signal amplification and improves device reliability
and energy consumption. RAM is the programmable
part of the device, holding information about patient-
related anti-bradycardia pacing, detection settings and
frequency thresholds. It contains a small amount of en-
ergy which is highly volatile. Some cases have been
reported wherein no obvious damage to the device was
found following irradiation, but the RAM had been en-
tirely erased [3].
CMOS circuitry is built from metal-oxide-semiconductor
field effect transistors. The metal oxide used in the CMOS
is polycrystalline silicon (Si) and silicon dioxide (SiO
2
)is
used as insulation. Energy deposition during radiother-
apy using ionising radiation can result in excess elec-
tron holes in the electron valence band and electrons
can leave their valence band (tunnelling). This can result
in aberrant electrical pathways and reprogramming of the
devices. Possible effects on the PM include altered sensi-
tivity, amplitude changes, telemetry and programming
* Correspondence: m.keshtgar@ucl.ac.uk
1
The Breast Unit, Academic Department of Surgery, Royal Free and University
College Medical School, Pond Street, London NW3 2QG, UK
Full list of author information is available at the end of the article
© 2012 Keshtgar et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.
Keshtgar et al. Radiation Oncology 2012, 7:128
http://www.ro-journal.com/content/7/1/128
defects (even preventing reprogramming), adjustment
of function or loss of function for seconds, days or
permanently.
Several cases have been reported where the threshold
programming was deleted or the devices failed at low
doses [1]. Therefore, in cases where the PM is close to
the treatment fields for external beam radiotherapy
(EBRT), adjustments may be necessary. These include
modification of the field size and shape, moving the PM
surgically out of the field or even withholding radiother-
apy in some cases.
An alternative to EBRT for these patients might be
intraoperative radiotherapy (IORT). The TARGIT trial-
ists group has reported the result of a randomised con-
trolled trial with this technique, which has confirmed
the safety and efficacy [4].
Case presentation
An 83 year old female patient presented with a two week
history of a self detected lump in the upper outer quad-
rant of the left breast. Clinically there was a 15 mm sus-
picious lump in the left breast, mammography did not
reveal any abnormality (R1) and ultrasound scan find-
ings were consistent with the diagnosis of breast cancer
(U5). Clinical and ultrasound examination of the axilla
was unremarkable. Core biopsy of the lesion confirmed
the diagnosis of invasive ductal carcinoma.
During review of her past medical history, it was
noted that in 1996 she had a cardiac PM inserted for
persistent sinus bradycardia. In 2003 this was replaced
with a St. Jude Medical dual chamber PM (St. Jude
Medical Inc., St. Paul, MN, USA). The pacemaker was
programmed to VVIR 70 bpm, hysterises 60 bpm in sin-
gle chamber mode due to an atrial lead failure. The
dominant rhythm was atrial fibrillation with intermit-
tent ventricular pacing. The patient’s heart rate varied
between 60–107 bpm. The patient had been self caring
and a recent transthoracic echocardiogram showed a
normal ejection fraction and left ventricular size. Ana-
tomically, the PM was located in a subcutaneous tissue
pocket in the upper pole of the left breast 9 cm away
from the primary tumour (Figure 1, Figure 2).
After discussion at the multidisciplinary meeting,
we recommended wide local excision and sentinel
node biopsy. In view of the size of the tumour and pres-
ence of the PM, it was also decided to offer the patient
intraoperative radiotherapy using the TARGIT technique.
Prior to surgery, the details of the PM were obtained
from the implanting hospital and the distance from the
tumour to the device was measured at an assessment
session. During surgery, after harvesting the sentinel
node and wide local excision, intraoperative radiotherapy
was performed using the Intrabeam
™
device (50 kV, Carl
Zeiss Surgical, Oberkochen, Germany). A 3 cm diameter
applicator was used, delivering approximately 20 Gy at
the surface of the breast tissue in direct contact with the
applicator, and 6 Gy at 1 cm from the surface, over a
time of 26 minutes. During the surgery, the radiation
Figure 1 Chest x-ray of the patient showing the pacemaker in
situ and the approximate position of the breast cancer.
Figure 2 Mammogram (mediolateral view) showing the
pacemaker. The breast cancer was mammographically occult.
Keshtgar et al. Radiation Oncology 2012, 7:128 Page 2 of 4
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dose to the PM was measured using thermoluminescent
dosimeters (TLD), which were placed on the edge of the
device closest to the x-ray source, and the distance be-
tween the applicator shaft of the Intrabeam and the PM
was recorded. The measured reading was converted to
dose using a batch calibration value corrected for supra-
linearity of dose response. The average reading of the
TLD packet was 0.08 Gy.
The patient tolerated the procedure very well and
there was no malfunction of the PM device during the
surgery or IORT. The patient made an uneventful recovery
and was discharged home the following day. The pace-
maker function was tested by the cardiology team before
and after treatment.
Histology confirmed the identification of a 14 mm
grade 2 invasive ductal carcinoma which was completely
excised. There was no lymphovascular invasion and the
sentinel node was free of tumour. The cancer was ER/PR
positive (quick score 8/8) and Her-2 negative. The pa-
tient was commenced on an Aromatase Inhibitor as an
adjuvant treatment.
Discussion
Although some centres treat patients in this age group
with surgery and adjuvant endocrine therapy alone,
within the TARGIT randomized trial there is no upper
age limit for the delivery of radiotherapy. This patient
would have been eligible to enter the trial were it not for
the contraindication to EBRT of a pacemaker so close in
distance to the tumour site. Moreover, this case is pre-
sented to highlight the issues concerning pacemakers
and radiotherapy and possible approaches to overcome
these problems.
As described in this case, the use of a short range kilo-
voltage energy x-ray source reduces the dose to normal
tissues and artificial devices which are sensitive to radi-
ation. By performing in vivo dosimetry using TLDs, we
confirmed a low radiation dose to the PM. Compared to
EBRT, during the IORT procedure the patient is closely
monitored by an anaesthetist. Furthermore, standard
monitoring such as ECG, pulse oximetry and blood pres-
sure monitoring would help to identify any arrhythmia
during the procedure. In some countries within Europe,
there is a requirement for the presence of a cardiologist
or a member of the cardiology team during or after IR
to ensure the correct functioning of a PM. This would
be reduced to a single visit for IORT in comparison to
daily visits for each fraction of EBRT.
At present, little is known about the effects of direct
and scattered radiation on PMs, especially the newer
PMs equipped with modern CMOS circuitry. However,
some manufacturers do provide estimates of the radi-
ation doses to which their PM models can be safely irra-
diated (e.g. St. Jude 20–30 Gy [5], Medtronic 5 Gy [6],
Guidant n.n. [7]). The wide range of these stated doses
and recent in-vitro data showing that a PM can fail at
any dose [8] pose significant challenges to radiation
oncologists treating patients with a PM. Therefore, tech-
niques like IORT using the Intrabeam device are an at-
tractive alternative to existing approaches. In addition,
the Intrabeam device does not produce electromagnetic
interference which is a concern with linear accelerators
and implantable cardioverter defibrillators [9]. Further
research into the safe tolerance doses for modern PM
devices will hopefully be translated into safer designs for
the future. In the meantime, however, we believe that
intraoperative radiotherapy using Intrabeam is a very
good option for selected patients with a pacemaker.
Conclusions
Intraoperative radiotherapy using the Intrabeam device
was successfully used to treat an invasive ductal carcin-
oma of the left breast with a cardiac pacemaker located
close in distance to the treatment area. This approach
may form a viable alternative to conventional radiotherapy
which has been shown to adversely effect such devices.
Consent
Written informed consent was obtained from the patient
for publication of this case report and any accompanying
images. A copy of the written consent is available for re-
view by the Editor-in-Chief of this journal.
Abbreviations
TARGIT: Targeted intraoperative radiotherapy; IR: Ionising irradiation, CMOS,
Complementary metal oxide semiconductor; PM: Pacemaker;
AAPM: American Association of Physicists in Medicine; AV: Atrio-ventricular;
RAM: Random access memory; EBRT: External beam radiotherapy;
IORT: Intraoperative radiotherapy; TLD: Thermoluminescent dosimeter;
ECG: Electrocardiogram.
Competing interests
The authors declared that they have no competing interest.
Authors’contributions
MK: conception and design; MK, DE, CR, KP: patient treatment; Consultation
on background and discussion of interpretation –MK, TD: surgical; KP, BG-F,
FW: radiation oncology, DE: physics; MK, BG-F: drafting manuscript; DE, CR,
KP, TD, FW: revising manuscript. All authors have read and approved the final
manuscript.
Author details
1
The Breast Unit, Academic Department of Surgery, Royal Free and University
College Medical School, Pond Street, London NW3 2QG, UK.
2
Department of
Radiotherapy, Royal Free Hospital, London, UK.
3
Department of Radiation
Oncology, University Medical Center Mannheim, University of Heidelberg,
Mannheim, Germany.
Received: 22 May 2012 Accepted: 19 July 2012
Published: 1 August 2012
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doi:10.1186/1748-717X-7-128
Cite this article as: Keshtgar et al.:Pacemaker and radiotherapy in breast
cancer: is targeted intraoperative radiotherapy the answer in this
setting?. Radiation Oncology 2012 7:128.
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