(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To report our experience in treating lung cancer patients with implanted cardiovascular devices (ICDs) using stereotactic body radiotherapy (SBRT).
Methods: During SBRT planning, the beam angle, energy, dose rate, and delivery method were carefully chosen to limit the maximum dose (D(max)) to the physician contoured ICD below AAPM’s (2.0 Gy for pacemakers and 1.0 Gy for defibrillators) and/or manufacturers’ recommendations. In vivo dosimetry and/or fractional function evaluation of the ICD may be ordered by the attending physician if the dose limit was not met and/or patients were device dependent. For each plan, the ICD D(max), the distance between the ICD centroid and the planning target volume (PTV) centroid (d(ICD-PTV)), and the shortest distance between the ICD and PTV edge in the longitudinal direction (d(Z)) were measured. Because some manufacturers also list dose rate limits, we estimated the maximum dose rate at the device for each patient.
Results: A total of 67 lung cancer patients with ICDs were treated using SBRT at our institute from 2010 to present. Only 6 MV flat or flattening filter free beams were allowed; dose rates ranged from 400 MU/min to 1,400 MU/min; coplanar and non-coplanar step-and-shoot IMRT, conformal arc, and VMAT delivery were used. Overall, the ICD D(max) averaged 0.6 ± 0.6 Gy. For 29 patients with ipsi-lateral ICDs and 10 of those patients treated for their upper lobe tumors, the ICD D(max) averaged 0.5 ± 0.7 Gy and 1.0 ± 0.6 Gy. The average d(ICD-PTV) and d(Z) were 17.3 ± 5.3 cm and 2.0 ± 6.1 cm. The mean dose rate at the ICD was 0.2 ± 0.3 Gy/min. No ICD malfunction was observed.
Conclusion: No ICD malfunction was reported at the D(max) levels and dose rates achieved.
Keywords
Quality Assurance, Treatment Planning, In Vivo Dosimetry
Taxonomy
TH- External beam- photons: Quality Assurance - VMAT
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