Staged gamma knife radiosurgery for large critically located benign meningiomas: evaluation of a series comprising 20 patients

Objectives: This study investigated the efficacy of staged radiosurgical treatment for intracranial meningiomas exceeding 3 cm in diameter. Methods: Between April 1992 and May 2008, staged gamma knife radiosurgery was performed in 20 patients with large benign meningiomas. 14 patients had undergone surgery at least once. The patients' ages ranged between 26 and 73 years (median 60.5). Tumour volumes measured between 13.6 and 79.8 cm(3) (median 33.3) and treatment volumes between 5.4 and 42.9 cm(3) (median 19.0). Of 41 treatments, the prescription dose at the tumour margin was 12 Gy for 33 treatments, 10 Gy for one treatment, 14 Gy for four treatments, 15 Gy for one treatment and 25 Gy for a further two treatments (median 12 Gy to a marginal isodose of 45%). Median follow-up was 7.5 years. Results: Tumour control was achieved in 90% of our series (25% tumour regression, 65% stable size). Two patients (10%) experienced tumour progression outlying the planning target volumes treated by an additional radiosurgical procedure. Thereafter tumour volume decreased in one patient and remained stable in the second one. Clinically, nine patients (45%) improved within the time of follow-up and 11 (55%) remained unchanged. Conclusion: As a result of excellent tumour control at a low concomitant morbidity, staged radiosurgical treatment for meningiomas represents a safe treatment modality that can be recommended for meningiomas in critical locations either after incomplete surgery or as primary treatment for patients with significant comorbidity.