Purpose: To evaluate the precision of hypofractionated radiosurgery using the Gamma Knife Extend relocatable system in patients with benign neoplasms located close to the optic pathways.
Methods and materials: A series of 59 irradiation procedures with the Extend system were performed on 12 patients. We treated 11 meningiomas and 1 craniopharyngioma. All patients except 1 were treated with 5 daily fractions of a 5-Gy margin dose; 1 patient was treated with 4 fractions of 6 Gy. The deviations on the X, Y, and Z axes were calculated as the mean value of all measures performed on each plate of the reposition check tool. An estimation of the patient's head motion during treatment was calculated as the difference between the radial deviations measured before and after each irradiation procedure.
Results: The maximum deviation of all measures was 0.9 mm for the 59 procedures. The mean deviations in the X, Y, and Z axes were 0.23 mm (standard deviation [SD], 0.17; maximum, 0.85), 0.31 mm (SD, 0.21; maximum, 0.90), and 0.27 mm (SD, 0.20; maximum, 0.80), respectively. The mean radial intrafraction difference was 0.16 mm (SD 0.14) and the maximum intrafraction deviation was of 0.7 mm. The mean follow-up duration was 19.3 months (range, 6-32 months). The visual status remained stable for 11 patients and improved in 1 patient; the tumor volume remained stable for 4 patients and decreased for 8 patients. From a clinical point of view, no new symptoms were recorded and no vision deterioration occurred.
Conclusions: The Extend system provides good repositioning accuracy and adequate immobilization of the patient's head for multisession treatment. The clinical and radiological outcomes of a series of 12 patients who underwent 59 irradiation fractions were excellent.
Copyright © 2015 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.