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Multi-Stage Stereotactic Radiosurgery Technique for Large Liver Tumor Using the Cyberknife System

C Ding

C Ding*, M Folkert , J Meyer , S Jiang , R Timmerman , The University of Texas Southwestern Medical Center, Dallas, TX


SU-I-GPD-T-606 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To develop a multi-stage stereotactic radiosurgery delivery technique for large liver tumor using the Cyberknife treatment platform.

Methods: A patient has a large (183 cm3) secondary liver tumor which was treated in fractionated treatment in linac was selected for this study. This large liver tumor was contoured and divided into 5 sub-targets with volumes ranging from 32.9-40.7cm3. Each sub-target is to be treated sequentially in each other day. The prescription dose was 25Gy to total target which is identical to prescription dose used in fractionated treatment. Cyberknife plans were retrospectively generated to treat the entire liver tumor with Xsight spine tracking. Inverse robotic radiosurgery treatment plans were generated for the total liver target volume and optimized to achieve 95% coverage. Staged plans for individual sub-targets were generated from the total liver target plan using the weighting MUs based on beam lengths within each sub-targets. Dose-volume analysis was used to evaluate the PTV coverage and normal tissue sparing.

Results: The sum-up physical dose of multi-stage sub-plans is identical to the planed whole target dose. The physical normal tissue dose is similar between fractionated dose to the multi-stage dose. Compared with fractional linac plan, the high dose to sub-target in multi-stage treatment has better ablative effect to target area.

Conclusion: The Cyberknife system can deliver a multi-staged conformal dose to treat large liver tumors. Target dose coverage and conformity as well as normal tissue toxicity measures were shown to be similar compared to that of fractionated treatment.

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