Safe classification of patients with CIED prior to RT of naso-/oropharyn- and esophageal carcinoma
Larissa Blümlein,
Germany
MO-0055
Abstract
Safe classification of patients with CIED prior to RT of naso-/oropharyn- and esophageal carcinoma
Authors: Larissa Blümlein1, Barbara Dobler1, Oliver Kölbl2, Ralf Ringler3
1University Hospital Regensburg, Radiotherapy - Medical Physics, Regensburg, Germany; 2University Hospital Regensburg, Radiotherapy, Regensburg, Germany; 3OTH Amberg-Weiden, Technical University of Applied Sciences, Medical Physics, Weiden i.d. Oberpfalz, Germany
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Purpose or Objective
Guidelines
such as DEGRO/DGK [1] or the Dutch guideline by Hurkmans et al. [2] classify
patients with cardiac implantable electronic devices (CIED) into risk groups
based on the dose to the CIED to avoid malfunctions due to ionizing radiation
such as inadequate pulse delivery. If CIED is located outside the radiation
field, dose calculation by treatment planning systems (TPS) is not sufficiently
accurate for safe classification. In
certain cases, a magnet is placed on the CIED for deactivation of
antitachyarrhythmia (ATA) therapy during treatment. The magnet is not included in the treatment planning. This leads
to further uncertainty in the dose determination at the CIED. Therefore, the
dose to the CIED has to be monitored by in-vivo dosimetry during the first
treatment. The aim of this study was to establish a strategy for accurate
classification of patients with esophageal or naso- and oropharyngeal carcinoma
into risk groups prior to first treatment.
Material and Methods
A
phantom was designed and manufactured for dose measurements at the implant by
TLDs and Gafchromic films. For 14 patients with esophageal or naso- and
oropharyngeal carcinoma, treatment planning was performed in the TPS Monaco
(Elekta, Sweden) using VMAT technique. Dose distributions of all plans were
calculated with and without a virtual magnet and compared. Measurements were
performed with the magnet on the surface of the phantom to assess the influence
of the magnet on the dose in the CIED. The measurements were compared to the dose
calculated with and without magnet and statistically evaluated.
Results
The
calculation without magnet in the TPS compared with the measurement with magnet
on the surface showed a dose underestimation about 15 % on average. The
comparison between calculated and measured dose with magnet on the surface
showed that the CIED dose is underestimated by about 14 % on average. According
to a confidence interval of 95 %, the true value is between 8 % and 20 % with a
probability of 95 % in both cases.
Conclusion
To ensure a safe classification of
patients into risk groups, the calculated dose in Monaco should be increased by
20 % for dose estimation prior to radiation therapy. For VMAT irradiations of
patients with esophageal or oro-/nasopharyngeal carcinoma, for which direct
irradiation of the CIED is avoided, placement of the magnet does not result in
significant impact on the CIED dose. Inclusion of the magnet in treatment
planning does not increase the accuracy of dose calculation in these cases.
[1] B. Gauter-Fleckenstein et al., “DEGRO/DGK
guideline for radiotherapy in patients with cardiac implantable electronic
devices,” Strahlentherapie und Onkologie : Organ der Deutschen Röntgengesellschaft", vol. 191, no. 5, pp. 393–404, 2015
[2] C.
W. Hurkmans et al., “Management of radiation oncology patients with a pacemaker
or ICD: a new comprehensive practical guideline in The Netherlands. Dutch
Society of Radiotherapy and Oncology (NVRO),” Radiation oncology, vol. 7, no. 1, p. 198, 2012