Gamma Knife Radiosurgery in Recurrent Glioblastoma

Abstract

Background: We evaluated Gamma Knife radiosurgery (GKRS) as a treatment option for patients with recurrent glioblastoma. Patients and Methods: 42 patients with histopathologically diagnosed recurrent grade IV tumor were treated with GKRS. All patients had undergone standard multimodal first-line treatment. The average time from diagnosis to GKRS was 17.0 months. The median target volume was 5.1 cm³. The median margin dose was 10 Gy and the median central dose 20 Gy. In a subset of patients, O⁶-methylguanine methyltransferase (MGMT) promoter methylation analysis by pyrosequencing was performed. Results: Most patients did not develop complications after GKRS. Time to radiological progression after initial GKRS was 4.4 months (95% CI: 3.1-5.7 months). Radiological progression mainly occurred beyond the GKRS-irradiated area. The median survival time after initial GKRS was 9.6 months (95% CI: 7.7-11.5 months). The median overall survival time from diagnosis was 25.6 months (95% CI: 21.8-29.3 months). Patients with MGMT promoter methylation survived significantly longer (33.4 months; 95% CI: 21.2-45.5 months) compared to patients without MGMT promoter methylation (16.0 months; 95% CI: 8.0-23.9 months). Conclusion: GKRS seems to be a relatively safe salvage treatment option for recurrent glioblastoma for highly selected patients but must be seen as part of a multimodal treatment algorithm.