Multisession Gamma Knife Radiosurgery for Orbital Apex Tumors

OBJECTIVE: This study was performed to analyze the outcome of multisession gamma knife radiosurgery (GKS) in benign tumors located at the orbital apex. METHODS: Medical records of 23 patients who underwent multisession GKS for benign orbital apex tumors were reviewed retrospectively. Three patients were diagnosed by histology, and the other 20 patients were given the diagnoses on the basis of clinical and radiological findings. Diagnoses included cavernous hemangioma (8 cases), meningioma (8 cases), and schwannoma (7 cases). All patients were treated with 4 sessions of GKS with 12 hours of interval. Median marginal dose in each session was 5 Gy (range, 4.5-5.5 Gy) at the 50% isodose line (range, 50%-55%). RESULTS: Mean clinical and imaging follow-up duration after treatment were 52.1 and 34.2 months, respectively. Tumor control was achieved in 22 patients (95.7%). Significant tumor shrinkage was observed in 17 patients (73.9%), and mean tumor volume reduction rate was 53.9%. Visual function was improved in 16 patients (69.6%) and stable in 4 patients (17.4%). Deterioration of visual acuity was reported by 3 patients (13.0%). Clinical and radiological response to multisession GKS was most excellent in cavernous hemangiomas with tumor control in all patients, and the mean tumor volume reduction rate was 68.3%. CONCLUSIONS: Multisession GKS proved to be an effective and safe management strategy for benign orbital apex tumors. Response to treatment was different according to the pathology, and multisession GKS may be considered as the initial treatment of choice for specific pathology such as cavernous hemangioma.