Stereotactic Gamma Knife Radiosurgery Technique For Very Large Volume Meningiomas Treatment. A Case Series.

Abstract

Background: Large intracranial meningiomas especially involving cranial base represent a significant treatment challenge and lead to increased morbidity and mortality. In some cases, large meningioma volume and proximity to critical structures reduce access to surgery and even hypofractionated radiosurgery. In this study, we evaluate safety and efficacy of the multistaged hypofractionated Gamma knife radiosurgery (MHGK) method for the treatment of very large meningiomas at our center. Methods: 6 female patients with progressing large-volume, an average of 36.32cm3, intracranial meningiomas after multiple craniotomies, and no previous intracranial radiotherapy were treated using this MHGK technique. 4 meningiomas were WHO grade I (3 meningothelial, 1 transitional), and histology of the other 2 meningiomas was unknown. Tumors were divided into two or three segments (average volume 17.76cm3) and treated prescribing 25Gy in 5 daily fractions with two-month gaps between each meningioma part. Treatment volumes were placed with 1-2 mm gap and areas of dose accumulation between treatment plans were directed away from critical structures. Results: Due to proximity to critical structures dose of 99% tumor volume was decreased to 21.49Gy on average (18.3 – 24.5Gy). During follow-up from 6 to 36 months (19 months’ average) all tumors showed volume shrinkage tendency. On average 8% of tumor volume decrease was observed after 6 months of follow-up. Two patients with a follow-up of 36 months showed a tumor volume decrease of 31%. During follow up no patient acquired acute or late treatment-related toxicities. Half a year after the treatment symptoms of 3 patients improved due to the decreased compression to the brain stem and other critical areas. Conclusions: Proposed treatment method for large-volume meningiomas shows promising results as an effective and safe treatment option for otherwise untreatable meningiomas. More patients and a longer follow-up are needed to verify the efficacy and safety of this treatment approach.