RADI-06. Gamma knife surgery for brain stem metastases

INTRODUCTION: Gamma Knife Surgery (GKS) is widely used for treatment of brainstem metastases (BSMs) with or without whole bran radiation therapy (WBRT). We hypothesized that BSMs treated with GKS using lower doses and omitting WBRT result in acceptable tumor control rates and low complication rates. METHODS: A retrospective single center study was performed to investigate the outcome following GKS of BSMs. All 33 patients with follow-up information treated with GKS for 39 metastases located in the cerebral peduncle, midbrain, pons or medulla oblongata were included in the study. The median treatment dose, defined as the lowest dose to 95% of the tumor volume, was 18 Gy. The tumor control rate as well as the survival time were related to a number of patients, tumor and treatment parameters. RESULTS: The local tumor control rate was 100% at one year and 89% at five years, and the overall median survival was 17 months. A good performance status and a treatable extracranial disease were favorably related to survival time. Two complications were observed, one lethal hemorrhage at the day of the treatment and one transient complication three months following GKS, resulting in a 6% complication rate at five years. Four of the 10 patient with symptomatic BSM improved clinically after GKS, while six remained unchanged. CONCLUSIONS: High local control and a low complication rates can be achieved using GKS for BSMs using lower doses as compared to brain metastases in other locations.