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Dosimetric Results of the First GammaPod Clinical Trial, GCC 1202: A 8 Gy Boost to the Lumpectomy Cavity

S Becker1*, Y Mutaf2 , Y Poirier1 , Y Niu3 , C Yu1,3 , B Yi1 , S Feigenberg4 , E Nichols1 , (1) university of Maryland School Of Medicine, Baltimore, MD, (2) Boston University Medical Center, Boston, MA, (3) Xcision Medical Systems, Columbia, MD, (4) University of Pennsylvania, Philadelphia, Pennsylvania


(Sunday, 7/29/2018) 3:30 PM - 4:00 PM

Room: Exhibit Hall | Forum 4

Purpose: The GammaPod (Xcision Medical Systems), a novel breast-specific stereotactic radiotherapy device has recently completed its first clinical trial and was granted 510k FDA clearance. The GammaPod dynamically dose-paints the target by rotating 36 non-overlapping Co-60 beams while the patient is translated continuously in three longitudinal. From simulation to treatment, the patient’s breast is immobilized using mild negative pressure through a stereotactic dual cup system with fiducials. The objective of this study is to conduct a dosimetric review of the patient’s treatment plans and evaluate the quality (e.g. conformity, uniformity) of plans generated by GammaPod TPS.

Methods: The GammaPod clinical trial successfully treated 15 of 17 patients. One patient did not meet the treatment criteria and another was unable to receive treatment due to an inability to maintain a negative pressure. Patients were prescribed 8 Gy to the lumpectomy cavity plus a 10mm PTV margin. The planning goals were PTV V100% ≥ 95% while minimizing dose to heart, skin, lung, and rib and maximizing dose uniformity inside the target. Patients then went on to receive whole breast radiation therapy using standard techniques.

Results: The PTV V�mean₎ = 66.9cc ± 29.9cc with a V�breast₎ = 1264.1cc ± 335.2cc. The average minimum (D98%), max (D2%) and mean doses were 7.7 Gy ± 0.4 Gy, 8.9 Gy ± 0.3 Gy, and 8.5 Gy ± 0.3 Gy, respectively. The average CI and HI were 1.4 ± 0.6 and 1.2 ± 0.0. The average D�max₎ for the heart, skin, lung, and chestwall were 1.0 Gy ± 0.7 Gy, 2.4 Gy ± 1.4 Gy, 0.9 Gy± 0.5 Gy, and 4.4 Gy ± 2.4 Gy, respectively. Mean treatment time for all cases was 25.8min ± 6.2.

Conclusion: GammaPod TPS is able to generate highly conformal SRS dose distributions to the breast while minimizing dose to normal tissue.


Breast, Stereotactic Radiosurgery, Dose Volume Histograms


TH- External beam- photons: Development (new technology and techniques)

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