Radiotherapy and pacemaker: 80 Gy to target close to the device

Umeå University
This is an accepted version of a paper published in Europace. This paper has been
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Citation for the published paper:
Kesek, M., Nyholm, T., Asklund, T. (2012)
"Radiotherapy and pacemaker: 80 Gy to target close to the device may be feasible."
Europace
URL: http://dx.doi.org/10.1093/europace/eus096
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Case report
Title
Radiotherapy and pacemaker: 80 Gy to target close to the device may be feasible.
Authors
Milos Kesek MD PhD1, Tufve Nyholm PhD2, Thomas Asklund MD PhD3
Departments of 1Medical Sciences and Heart Centre, 2,3Radiation Sciences and Oncology,
Umeå University, Umeå, Sweden
Corresponding author
Milos Kesek, Heart Centre, University Hospital, S-901 85 Umeå, Sweden,
telephone: (46) 90 7850000, fax (46) 90 127630
E-mail: [email protected]
1
Summary
Modern pacemakers using complementary metal-oxide semiconductors (CMOS)-technology
are sensitive to radiation. The guidelines recommend caution at doses above 2 Gray (Gy).
Repositioning should be discussed if cumulative dose and dose rate exceeds 10 Gy and 0.2 Gy
min-1.
We report a case of a man with mechanical mitral valve prosthesis and pacemaker due to sick
sinus syndrome (Vitatron T20®). Five years later, a left-sided lung cancer was diagnosed.
Radiotherapy was planned. Moving the pacemaker out of the radiation field would require
either use of a lead extender and tunneling or implantation of third electrode through the right
subclavian vein already occupied by a venous port. The pacemaker was left in site and the
patient received hyperfractionated intensity modulated radiotherapy with 1.6 Gy twice daily
to a total dose of 80 Gy. The calculated maximum, minimum and mean doses to the
pacemaker were 48 Gy, 9 Gy and 25 Gy, respectively. For short periods, the pacemaker
received up to 7 Gy min-1 through direct radiation. At control afterwards, the technical
parameters were normal. The radiation dose significantly exceeded the pacemaker guidelines.
The circuits in Vitatron T20®, similar to current Medtronic®, Sorin® and Boston Scientific®
devices have thin CMOS-gates (≤ 1.5 µm). This may contribute to their resistance to
irradiation. The approach must however be carefully individualized. Leaving the pacemaker
in place during high dose radiotherapy can be considered if the patient is not pacemakerdependent and the drawbacks of a repositioning are significant.
2
Abstract
A 65 years old man with mechanical mitral valve prosthesis and pacemaker developed a
leftsided lung cancer. He received radiation therapy to a total dose of 80 Gy. The pacemaker
was left in place and showed no signs of malfunction after the therapy.
3
Case report
Modern pacemakers using complementary metal-oxide semiconductors (CMOS)-technology
are sensitive to radiation. The guidelines recommend avoidance of pacemaker exposure to the
unshielded beam and caution at doses above 2 Gray (Gy) (1)(3). Repositioning should be
discussed if the cumulative dose and dose rate exceeds 10 Gy (2) and 0.2 Gy min-1 (3).
We report a case of a 65 years old man with a mechanical mitral valve prosthesis. In 1994 a
DDD-pacemaker was implanted due to sick sinus syndrome (Vitatron Diamond® 800,
connected to two Medtronic® 4023 unipolar electrodes with passive fixation). The patient
developed atrial fibrillation and when the pacemaker reached ERI in 2005 it was electively
replaced by a single chamber device (Vitatron T20®).
Five years later, a cancer was diagnosed in the left superior pulmonary lobe and mediastinum
in immediate proximity of the pacemaker (figure 1). Chemotherapy was given through a
right-sided venous port and radiotherapy was planned. Moving the pacemaker out of the
radiation field would require either use of a lead extender and tunneling or implantation of a
third electrode through the right subclavian vein already occupied by the venous port. As
pacing need was modest, we decided to complete radiotherapy with the pacemaker left in site.
The initial test values were normal. The pacemaker was reprogrammed to 000-mode under
initial telemetry supervison. During the following two weeks, the patient was followed at the
outpatient clinic, with no bradycardia-related symptoms.
The patient subsequently received hyperfractionated intensity modulated radiotherapy with
1.6 Gy twice daily in 50 fractions during 5 weeks to a total dose of 80 Gy with 6 opposing
fields in 43 segments using a 6 megavolt photon beam. The calculated maximum, minimum
and mean doses to the entire pacemaker were 48 Gy, 9 Gy and 25 Gy, respectively. The
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pacemaker was exposed to direct radiation in one of the beams, thus receiving up to 7 Gy
min-1 for short periods. A pacemaker control during this period showed unchanged normal
values. At control immediately after the radiotherapy, the technical parameters were normal
(threshold 0.625V, electrode impedance 400 ohm, battery impedance 400 ohms). A
measurement one year later showed unchanged values (threshold 0.5V, electrode impedance
450 ohm, battery impedance 0.5 kohm).
We present an uncomplicated case of a pacemaker receiving a radiation dose significantly
exceeding the guidelines (1). Several reports describe adequate pacemaker function after
irradiation with 45-70 Gy close to the device (4-6). A review describes device malfunction in
less than 30% after radiation therapy (7). Pacemakers with thin CMOS gates are relatively
resistant. At a cumulative in-vitro dose of 246 Gy, five of six 3 ug devices were operative (but
none of the older 5 and 8 um devices) (8). However, to our knowledge, no clinical report has
previously described a dose to target of 80 Gy close to the pacemaker. The circuits in Vitatron
T20®, similar to current Medtronic®, Sorin® and Boston Scientific® devices have a gate
thickness of ≤ 1.5 µm, which may be one explanation for their relative resistance to
irradiation. The approach must however be carefully individualized. The decision to leave the
pacemaker in place during high dose radiotherapy can be considered if the patient is not
pacemaker-dependent and the drawbacks of a repositioning are significant.
5
References
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implanted cardiac pacemakers: report of AAPM Task Group No. 34. American Association of Physicists in
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pacemaker operation. Phys Med Biol 2002;47(16):2879-93.
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Legend Figure 1.
A 3-D volume-reconstruction of the planning target volume (PTV) dose-field. The
pacemaker, the right ventricular electrode and the right atrial electrode (disconnected and
isolated) are seen immediately outside the field volume. The venous port enters the upper
caval vein through the opposite subclavian vein.
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