Evaluation of Dose-Staged Gamma Knife Radiosurgical Treatment Method for High-Risk Brain Metastases.

Objectives: The study aim was to evaluate the utility of 2-fraction, dose-staged Gamma Knife radiosurgery (GKRS) in patients with large, high-risk brain metastases (BMs).

Methods: A total of 63 large BMs in eloquent areas in 61 patients were treated with GKRS in 2 reduced doses. Treatment planning was conducted on the 50% isodose line and included the whole tumor volume as seen on T1 contrast-enhanced and T2-weighted magnetic resonance imaging sections. The median margin and central dose were 12 Gy and 24 Gy, respectively, for both fractions. Patients were assessed using the Graded Prognostic Assessment, Recursive Partitioning Analysis, and Score Index for Radiosurgery.

Results: Thirty-two patients (53%) had been diagnosed with multiple BMs, and extracranial metastases were present in a majority of patients before GKRS treatment. Significant decreases in tumor volume were observed between the first and second treatment stages. At 3-month follow-up, a majority of patients presented with stable or decreased lesion volumes. The remaining patients showed intralesional hemorrhaging or increasing edema that was managed conservatively. Three patients were diagnosed with tumor progression at the last follow-up and received microsurgical treatment. The median time to radiologic progression was 7 months. The median survival time after initial BM diagnosis was 6 months. Survival times were significantly longer than 3 of 4 calculated prognostic survival estimates.

Conclusion: The new 2-fraction, dose-staged GKRS concept seems to be a well-tolerated and effective treatment option for large BMs. This method may be indicated in elderly patients or patients with surgical contraindications with large or high-risk brain metastases.