Volume not number of metastases: Gamma Knife radiosurgery management of intracranial lesions from an Australian perspective

Background and purpose: To assess the response of the first cohort of patients treated with Gamma Knife radiosurgery in Australia. Materials and methods: A prospectively collected cohort of 180 patients with intracranial metastases from different primaries was treated between August 2010 and July 2017. Survival was calculated using the Kaplan–Meier's method. Cox regression was used for multivariate analysis. Results: Currently 141 patients (78.3%) have died of their disease. The median survival for the group as a whole was 9.2 months, with observed differences resulting from the volume of tumor burden (11.4 months for volumes <3.2 cm ³ to 5.16 months for volume >9.1 cm ³ ). Overall 2-year survival was 20.7%. Conclusion: Results from the first Gamma Knife radiosurgery center in Australia showed that the treatment is feasible and effective, consistent with the international experience. For patients with larger numbers of intracranial metastases, the total volume of the intracranial burden may be of more significance in predicting outcomes. While there appeared to be a difference in survival by histologic origin, this could be related to concurrent systemic immunotherapy available for certain tumors.