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- Title
Evaluation of biological effective dose for Gamma Knife staged stereotactic radiosurgery for large brain metastases.
- Authors
Cui, Taoran; Weiner, Joseph; Danish, Shabbar; Chundury, Anupama; Ohri, Nisha; Ning Yue; Xiao Wang; Ke Nie
- Abstract
Objective: Gammaknife (GK) staged stereotactic radiosurgery (Staged-SRS) has emerged as an effective treatment option for large brain metastases (BMs) (> 2cm in diameter or > 4 cc in volume) with encouraging clinical results. However, because of the tumor shrinkage observed between two sessions of Staged-SRS, it has been challenging to evaluate the overall total composite treatment dose. This study aims to develop a novel workflow to evaluate the total biological effective dose (BED) delivered to both the tumor and normal brain tissue in Staged-SRS and to compare those in single fraction SRS (SF-SRS) and hypo-fractionated SRS (HF-SRS) treatment. Methods: Patients treated with GK Staged-SRS at a single institution were retrospectively included. Deformable image registration was performed for MRI images acquired at each session using commercial software to account for tumor shrinkage. The dose delivered in two staged sessions was then summed based on the registration and the total BEDs to tumor/ normal brain tissue of Staged-SRS were computed using the linear-quadratic model with and without considering cell repopulation during session interval. Each patient was also replanned for SF-SRS and HF-SRS where the BEDs were computed using the same formalism. Tumor BED98% and brain V84Gy2, which was equivalent to V12Gy commonly assessed in SF-SRS, were compared between SF-SRS, HF-SRS, and Staged-SRS plans with the Wilcoxon Rank Sum test. Results: Twelve patients with a total of 24 BMs treated with GK Staged-SRS were retrospectively identified. We observed significant differences (p<0.05) in tumor BED98% but comparable brain V84Gy2 (p=0.677) between the Staged-SRS and SF-SRS plans. No dosimetric advantages of Staged-SRS over HF-SRS were observed. Tumor BED98% in the HF-SRS plans were significantly higher than those in the Staged-SRS plans (p<0.05). Despite the additional 1-mm setup margin added to the tumor with resultant larger PTV, brain V84Gy2 in the HFSRS plans remained lower (p< 0.05). Conclusion: We presented a novel approach to calculate the composite BEDs delivered to both tumor and normal brain tissue for Staged-SRS. Compared to SFSRS, Staged-SRS delivers a higher dose to tumor but comparable dose to normal brain tissue. In addition, our results didn’t show any dosimetric advantages of Staged-SRS over HF-SRS.
- Subjects
STEREOTACTIC radiosurgery; IMAGE registration; MAGNETIC resonance imaging; ACCOUNTING software; BRAIN tumors
- Publication
Journal of Radiosurgery & SBRT, 2022, Vol 8, p66
- ISSN
2156-4639
- Publication type
Article