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Feasibility of a Novel Method for Single Isocenter Treatment of Multiple Brain Metastases Patients

S Jupitz

S Jupitz1*, S Braunstein2 , L Ma3 , A Perez-Andujar4 , (1) ,St. Marys College of Maryland, St. Marys City, MD, (2) University of California San Francisco, San Francisco, California, (3) UCSF Comprehensive Cancer Center, San Francisco, CA, (4) University of California San Francisco, San Francisco, CA


SU-I-GPD-T-602 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare a novel method for single isocenter Linac stereotactic radiosurgery (SRS) to GammaPlan Frame-fixed SRS for patients with multiple (5-10) brain metastases

Methods: Fifteen patients previously treated with Gamma Knife (GK) Perfexion were used in this study. Each patient had 5-10 brain metastases (total 100 lesions) treated in a single session. New plans were constructed using the Multiple Brain Metastases Elements (MME) software for Varian TrueBeam STx treatments with the same prescription dose to the target as GK. We evaluated the mean total brain dose and brain volume receiving 12 Gy (V12). The Paddick conformity (CI) and gradient (GI) indices were used to evaluate the conformity and dose fall-off, respectively.

Results: Preliminary data shows a marginal increase in mean brain dose for Elements plans. The V12 region was lower for GK by 5 cc on average. Conformity between the systems was comparable for each lesion as well as per plan, with Gamma Knife CI (mean 0.51 +/- 0.19) slightly degraded with decreasing lesion volume while Elements CI (mean 0.55 +/- 0.19) remained more consistent. The gradient index (GI) of 50% to 100% prescription generally favored GK with an average difference of 2.40 +/- 2.07 (23 +/- 17%) between plans. We calculated an additional GI for the 30% to the 60% dose region, which was lower for both modalities with an average difference of 0.14 +/- 0.36 for GK and 4 +/- 10% for MME per plan.

Conclusion: MME demonstrated comparable plan quality to GK for multiple brain metastases, with normal brain V12 and mean brain doses similar to those delivered by GK. MME produced consistent conformity and achieved steep dose falloff outside the target. Therefore, Brainlab Elements may provide a suitable alternative for treatment centers wishing to perform Linac-based SRS treatments without access to devices such as GK.

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