GAMMA-KNIFE FOR GLIOMA - SELECTION FACTORS AND SURVIVAL

Purpose: To determine factors associated with survival differences in patients treated with radiosurgery for glioma. Methods and Materials: We analyzed 189 patients treated with Gamma Knife radiosurgery for pri mary or recurrent glioma World Health Organization (WHO) Grades 1-4. R esults: The median minimum tumor dose was 16 Gy (8-30 Gy) and the medi an tumor volume was 5.9 cc (1.3-52 cc). Brachytherapy selection criter ia were satisfied in 65% of patients. Median follow-up of all survivin g patients was 65 weeks after radiosurgery. For primary glioblastoma p atients, median survival from the date of pathologic diagnosis was 86 weeks if brachytherapy criteria were satisfied and 40 weeks if they we re not (p = 0.01), indicating that selection factors strongly influenc e survival. Multivariate analysis showed that increased survival was a ssociated with five variables: lower pathologic grade, younger age, in creased Karnofsky performance status (KPS), smaller tumor volume, and unifocal tumor. Survival was not found to be significantly related to radiosurgical technical parameters (dose, number of isocenters, prescr iption isodose percent, inhomogeneity) or extent of preradiosurgery su rgery. We developed a hazard ratio model that is independent of the te chnical details of radiosurgery and applied it to reported radiosurger y and brachytherapy series, demonstrating a significant correlation be tween survival and hazard ratio. Conclusions: Survival after radiosurg ery for glioma is strongly related to five selection variables. Much o f the variation in survival reported in previous series can be attribu ted to differences in distributions of these variables. These variable s should be considered in selecting patients for radiosurgery and in t he design of future studies. Copyright (C) 1996 Elsevier Science Inc.