Long-term outcomes following Gamma Knife radiosurgery for small, newly diagnosed meningiomas

Abstract

Object: Although stereotactic radiosurgery were established as an effective treatment modality for intracranial meningiomas, there have been no comprehensive studies focused on long-term outcomes and histologic results for purely small-sized meningiomas after radiosurgery. Therefore, we investigated long-term outcomes and histology of small-sized meningiomas after radiosurgery.

Methods: The authors reviewed the data retrospectively of a total of 920 patients treated with single-session Gamma Knife radiosurgery with intracranial meningioma (Radiosurgery center, Asan Medical Center). After stratifying meningiomas by size, it was defined as small-sized meningiomas less than 1000 mm(3) in tumor volume. The patients with newly diagnosed small-sized meningiomas were enrolled in this study (113 patients). All patients had a minimum follow up of 12 months (12-120 months), clinical symptoms and brain MRI were checked by neurosurgeons. When the tumors grew readily with newly developed neurologic symptoms, microsurgical resection was performed. Histologic analysis was done with resected tumors by neuropathologists.

Results: Among 113 patients, 9 patients (7.9%) showed the increased tumors with clinical symptoms after radiosurgery, followed by microsurgical resection in 4 patients (3.5%). The other 5 (4.4%) patients showed that the size of tumor slightly increased after GKRS that is transient. Interestingly, the histologic results of resected meningiomas due to increased volume after radiosurgery were all revealed as WHO grade II meningiomas (1 clear cell type and 3 atypical meningiomas). Although the histologic confirmation was performed only in 4 patients underwent surgery, it is interesting that all tumors readily grew after radiosurgery were high grade meningiomas.

Conclusion: In this study, we revealed the long-term outcomes of small meningiomas following stereotactic radiosurgery in the aspect of tumor control. The tumor control rate of radiosurgery in small meningiomas reached to 92.1% and there were perilesional edema in 6.1%. The 7.9% of tumors grew readily and 3.5% were finally underwent microsurgical resection. The histologic results were all WHO grade II meningiomas (1 clear cell and 3 atypical meningiomas).

Keywords: Gamma Knife; Histology; Small meningioma; Stereotactic radiosurgery.