Gamma Knife Radiosurgery for Benign Meningioma: Significance and Therapeutic Potential

Abstract

This review elucidates the value and the therapeutic spectrum of gamma knife radiosurgery (GKRS) for benign meningiomas based on results obtained at our department. Between April 1992 and May 2008 38.8% (394/1,016 patients) of patients with benign meningioma underwent primary single session GKRS. Staged GKRS was performed in 20 patients with large critically located meningiomas, 14 of whom having undergone surgery at least once. The patients’ age ranged between 26 and 73 years (median 60.5). For single session GKRS median tumor volume was 6.5 cm³, median prescription dose at the tumor margin (covered by a median isodose of 45%) was 12 Gy. Median tumor volume treated by staged GKRS measured 33.3 cm³ and median treatment volume 19.0 cm³. For 41 treatments, the median prescription dose at the tumor margin was 12 Gy. Median follow-up for staged GKRS was 9.4 years.

For single treatment GKRS, the actuarial progression-free survival rate was 98.5% at 5 years and 97.2% at 10 years at a (mostly temporary) complication rate of 4.5%. In patients undergoing staged GKRS, primary tumor control was achieved in 90%. Two patients (10%) with tumor progression outlying the planning target volumes experienced tumor control after an additional radiosurgical procedure. Clinically, 45% of all patients improved within the time of follow-up, 55% remained unchanged. Radiosurgery is a neurosurgical domain that offers results comparing favorably to radical surgery for meningiomas of small to medium-size in critical locations. For larger critically located meningiomas, a combination of judicious surgery and radiosurgery yields the best functional outcome. Staged GKRS provides a substantial therapeutic improvement for large otherwise untreatable meningiomas.