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. 2021 Mar;22(3):8-15.
doi: 10.1002/acm2.13127. Epub 2021 Mar 3.

Reproducibility of a novel, vacuum-assisted immobilization for breast stereotactic radiotherapy

James W Snider  1 , Elizabeth M Nichols  2 , Yildirim D Mutaf  3 , Shifeng Chen  2 , Jason Molitoris  2 , Tejan Diwanji  4 , Stewart J Becker  2 , Steven J Feigenberg  5
Affiliations

Reproducibility of a novel, vacuum-assisted immobilization for breast stereotactic radiotherapy

James W Snider et al. J Appl Clin Med Phys. 2021 Mar.

Abstract

A novel, breast-specific stereotactic radiotherapy device has been developed for delivery of highly conformal, accelerated partial breast irradiation. This device employs a unique, vacuum-assisted, breast cup immobilization system that applies a gentle, negative pressure to the target breast with the patient in the prone position. A device-specific patient loader is utilized for simulation scanning and device docking. Prior to clinical activation, a prospective protocol enrolled 25 patients who had been or were to be treated with breast conservation surgery and adjuvant radiotherapy for localized breast cancer. The patients underwent breast cup placement and two separate CT simulation scans. Surgical clips within the breast were mapped and positions measured against the device's integrated stereotactic fiducial/coordinate system to confirm reproducible and durable immobilization during the simulation, treatment planning, and delivery process for the device. Of the enrolled 25 patients, 16 were deemed eligible for analysis. Seventy-three clips (median, 4; mean, 4.6; range, 1-8 per patient) were mapped in these selected patients on both the first and second CT scans. X, Y, and Z coordinates were determined for the center point of each clip. Length of vector change in position was determined for each clip between the two scans. The mean displacement of implanted clips was 1.90 mm (median, 1.47 mm; range, 0.44-6.52 mm) (95% CI, 1.6-2.20 mm). Additional analyses stratified clips by position within the breast and depth into the immobilization cup. Overall, this effort validated the clinically utilized 3-mm planning target volume margin for accurate, reliable, and precise employment of the device.

Keywords: breast cancer; stereotactic radiotherapy.

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Conflict of interest statement

Snider reports conflicts related to the Maryland Industrial Partnerships grant which has funded device development and research for the GammaPod device. Feigenberg and Nichols report the same conflict. Nichols and Becker report speaking for and representing Xcision Medical Systems who developed and market the GammaPod device. Nichols is the primary investigator for clinical trials investigating the application of the GammaPod device.

Snider reports unrelated conflicts including honorarium, consulting, and travel expenses from Varian Medical Systems, Siemens Healthineers, and the Society for Thermal Medicine. Snider reports an unrelated patent regarding a proton radiotherapy planning methodology.

All above sources of bias have been effectively mitigated in this investigation through systematic methodology for data collection and analysis.

Figures

FIG. 1
FIG. 1
Breast stereotactic radiotherapy device
FIG. 2
FIG. 2
Entire cohort clip displacement distance from CT1 to CT2 for individual clips (n = 16 patients, 73 clips), with 95% CIs (black lines)
FIG. 3
FIG. 3
Individual clip displacement distance from CT1 to CT2 for patients without cup pressure loss (n = 12 patients, 55 clips), with 95% CIs (black lines)
FIG. 4
FIG. 4
Patient with substantial positioning difference between CT1 and CT2 examinations. Note the folded right arm (blue arrow) in CT2 (b and d) vs. initial CT1 position (a and c) on two representative axial slices (a vs. b, c vs. d), which has substantially changed the external contour (green, all images) and rotated the patient. Also note that the clips immediately surrounding the lumpectomy cavity remain relatively unchanged (a and b)
See this image and copyright information in PMC

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