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GammaPod Versus Cyberknife: A Dosimetric Comparison of Stereotactic Radiotherapy for Early Stage Breast Cancer as An APBI Modality

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X Zhu

X Zhu1*, Y Niu2 , S Lei1 , J W Lischalk1 , G Zhang1 , (1) Georgetown University Hospital, Bethesda, MD, (2) Xcision Medical Systems, Columbia, MD


SU-I-GPD-T-378 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Accelerated partial breast irradiation (ABPI) has become an accepted treatment regimen for many woman with favorable risk early stage breast cancer. Many radiation modalities currently exist to deliver ABPI. GammaPod and the CyberKnife radiosurgical system are two modern and novel radiosurgical modalities with feasibility for ABPI delivery. In this dosimetric comparison study we report the target coverage and normal tissue sparing for these two radiosurgical systems in the treatment of early stage breast cancer.

Methods: Five patients with early-stage breast cancer treated initially with surgical resection were included within this trial. Planning CT scans were obtained with prone position. GTV was contoured around lumpectomy cavity, and expanded by 1 cm to PTV. 95% of the PTV was planned to receive a single fraction of 8 Gy, and maximum point dose was not to exceed 9.6 Gy. Kernel-based treatment planning system of GammaPod optimizes dynamic paths of couch movement employing “travelling salesman” algorithm. The cyberknife plans were optimized using stepwise multi-criteria optimization, using both prone and supine setup.

Results: For GammaPod, the average and standard deviation of PTV conform index is CI=1.20 ± 0.14, the homogeneity index HI=1.14 ± 0.02. Dmax=1.16 ± 0.82 Gy for the lung, Dmax=1.45 ± 0.83 for the heart, and the treatment time is 11.3 ± 3.80 min. For Cyberknife with supine setup, CI=1.11 ± 0.05, HI=1.15 ± 0.05, Dmax(lung)=1.03 ± 0.54 Gy, Dmax(heart)=1.06 ± 0.57 Gy, and the treatment time is 25.6 ± 2.7 min. For Cyberknife with prone setup, CI=1.22 ± 0.14, HI=1.18 ± 0.05, Dmax(lung)=2.07 ± 0.09 Gy, Dmax(heart)=2.18 ± 0.18 Gy, and the treatment time is 34.2 ± 2.3 min.

Conclusion: Both GammaPod and Cyberknife can provide clinic acceptable stereotactic radiotherapy plan for the breast treatment. However, GammaPod employs optimized beam arrangements designed for a patient’s prone setup, it features faster delivery.

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