Joana S. Emmolo MD, Presenter: Nothing to Disclose

Nokul Panigrahi PhD, Abstract Co-Author: Nothing to Disclose

Nanemeka C. Ikoro PhD, Abstract Co-Author: Nothing to Disclose

Hani L. Ashamalla MD, Abstract Co-Author: Nothing to Disclose

Purpose/Objective(s): With the rise in use of ICDs there is a relative increase in the incidence of cancer patients who are referred for radiation therapy (RT) and have a device in place. This poses a difficult situation in regards to treatment planning given the unclear effect of radiotherapy on ICDs. Materials/Methods: Three patients (pts) with ICDs were treated with RT at our institution. The cases consisted of two lung and one prostate cancer. Conformal treatment planning was utilized for lung and IMRT for prostate. The median total dose delivered was 67.8Gy (59.4-79.2Gy). All pts underwent in-vivo dosimetry. The distance of the closest edge of the ICD and the edge of the radiation field was recorded. In one patient, the ICD needed to be relocated to the contralateral infraclavicular area as it was overlying the PTV. In addition, in-vitro dose measurements were performed in a constructed phantom simulating the location of the ICD. CT-based planning was performed and ICDs were included as ?organs at risk? for dosimetry. All pts were required to have their ICD interrogated prior to the beginning of their treatment as well as once weekly throughout the course of their therapy. Results: There was no ECG changes or ICD malfunctions recorded. Interrogation of the devices confirmed no changes in the programmed parameters. The mean direct measured dose in the 2 lung pts who had devices at ó20 cm was 3.6cGy/180 cGy /fraction compared to 0.1 cGy in the prostate case at >20 cm. The individual mean cumulative doses to the devices were 172.8, 75.2 and 7.9cGy from 6480, 5940 &7920 cGy respectively. The cumulative in-vitro phantom measurements contributed from 6480 cGy was 81 at 10 cm and 29.2cGy at 20 cm from the mock device. Recorded dose at 42 cm for 7920cGy was 11.1 cGy. Proposed Guidelines: For ICDs located at a distance ò 20cm, no deactivation is required: ICD interrogation to be done prior to and at the end of therapy. In cases where the ICDs are located ó 20 cm from the edge of the field: 1) Magnetically deactivate the device during treatment. 2) Calculate the cumulative scattered doses, including dose contributed by portal imaging. 3) Maintain cumulative dose below 500cGy. 4) Avoid treatment beams and portal imaging directly through the ICDs. 4) Monitor patient?s cardiac status using ECG daily in the presence of a physician. 5) Interrogate ICD once weekly. Conclusions: There is a potential for malfunction from direct and scattered radiation in patients with ICDs, particularly in those ó 20 cm away from the closest treatment field. In our experience, the individual ICD mean cumulative doses were 172.8cGy and 75.2cGy for the lung pts requiring adherence to the guidelines detailed above. For devices beyond 20 cm of the RT field, the cumulative dose was 7.9cGy, requiring less stringent guidelines.

Emmolo, J, Panigrahi, N, Ikoro, N, Ashamalla, H, Effects of Therapeutic Radiation on Implantable Cardioverter Defibrillators (ICDs).  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8501049.html