Correlation Based on the WHO Grading with Tumor Control and Clinical Outcome Following Gamma Knife Radiosurgery in Meningiomas

Background and Aim: The aim of this study was to study the effect of Gamma Knife (GK) on meningiomas based on the World Health Organization's (WHO) grading system in terms of tumor control and final clinical outcome. Methodology: This retrospective study included clinicoradiological and GK characteristics of patients who had undergone GK for meningiomas at our institute from April 1997 until December 2009. Results: Of 440 patients, 235 underwent secondary GK for residual/recurrent lesion and 205 received primary GK. Of the 137 patients whose biopsy slide could be reviewed, 111 patients had grade I, 16 had grade II, and 10 had grade III meningiomas. Good tumor control rates were seen in 96.3% of grade I meningioma patients, 62.5% of 16 grade II, and 10% of grade III meningioma patients at median follow-up of 40 months. Age, sex, Simpson's grade of excision, and increasing peripheral dose of GK did not affect the response to radiosurgery (P > 0.05). Multivariate analysis showed that high-grade tumor and radiotherapy prior to GK were important negative predictors for progression of tumor size after GK radiosurgery (GKRS) (P < 0.05). In patients with WHO grade I meningioma, radiation therapy prior to GKRS and repeat surgery were predictors for poorer outcome. Conclusion: In WHO grades II and III meningiomas, no factors affected tumor control except the histology itself.