Two-Staged Stereotactic Radiosurgery For The Treatment Of Large Brain Metastases: Single Institution Experience And Review Of Literature

Introduction: Two-staged stereotactic radiosurgery (SRS) has been shown as an effective treatment for brain metastases that are too large for single fraction SRS.Methods: Patients with large brain metastases (>4 cm(3)) treated with two-staged SRS from January 2017 to December 2019 at our institution were retrospectively identified.Results: There were 23 brain metastases treated. The normal brain volume receiving equivalent 12Gy-in-single-fraction was defined as V-12E. The V-12E for original single-fraction GKS plan (mean of 41.4 cm(3), range 5.6-146.1 cm(3)) was significantly higher compared to that of the second stage (mean of 23.7 cm(3), range 2.8-92.7 cm(3)). The median tumor volume measured at the second stage (4.30 cm(3)) was reduced by an average of 52.2% compared to the first stage (9.58 cm(3)). Three patients (27.3%) showed local tumor progression in 4 tumors (20%). The median time to progression was 152 days.Conclusions: Two-staged SRS is an effective treatment technique for large brain metastasis that results in significant reduction of tumor volume at the second stage SRS. Optimal treatment dose has not yet been defined.