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SRS for Treating Multiple Brain Metastases Using CyberKnife After Whole Brain Irradiation

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P Desai

P Desai1*, B Caroprese2 , J Gilroy3 , N Andrade4 , (1) East Texas Medical Center, Tyler, TX, (2) East Texas Medical Center, Tyler, TX, (3) East Texas Medical Center, Tyler, texas, (4) Tyler Neurosurgical Associates, Tyler, Texas


SU-I-GPD-T-630 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: SRS is offered to control brain metastases as an alternative to whole brain irradiation (WBI). In some cases WBI is required even after SRS if multiple brains metastases occur in other parts of the brain. It is challenging for clinicians to treat new metastases after multiple courses of SRS and WBI. We discuss a strategy of performing SRS to multiple brain metastases after previous SRS and WBI. Although typical SRS doses are single fraction doses between 1600cGy and 2400cGy we recommend slightly lower single fraction doses of 1500cGy which enable us to lower the chances of causing radiation necroses.

Methods: Accuray CyberKnife (G-3), Multiplan V5.2.1 treatment planning system. The patient’s imaging studies are sent to the Multiplan system. The neurosurgeons and radiation oncologist at our site contour the GTV and the relevant critical structures. A treatment plan for each PTV (GTV+1mm margin) is generated using iterative planning and custom planning structures. Separate plans deliver 1500cGy to each PTV using fixed collimators which enable us to spare surrounding brain tissue due to the higher dose gradients at the PTV and normal brain interface. The upper limit to the number of lesions treated is dictated by the integral dose to the whole brain. We have thus far treated 10 lesions in a single case using this scheme.

Results: Post treatment follow-up imaging done at 3, 6 and 12 months shows gradual diminishing and obliteration of the lesions. There is also a possibility of treating future new lesions with this dose.

Conclusion: We conclude that this scheme of treating multiple brain metastases is an effective and safe treatment.

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