Role of Gamma Knife surgery for intracranial atypical (WHO Grade II) meningiomas

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Atypical meningioma often recurs even after resection. As a salvage modality, radiotherapy or stereotactic radiosurgery (SRS) is attempted for this aggressive tumor. This retrospective study was performed to evaluate the efficacy of SRS that involved Gamma Knife surgery (GKS) for atypical meningioma.


The authors reviewed records from 22 patients with histologically proven atypical meningioma who underwent GKS for 28 lesions at the authors' institute. The median patient age was 70 years (range 24–91 years), and the median tumor volume for each procedure was 6.0 cm3 (range 1.6–38.7 cm3). The margin dose ranged from 14 to 20 Gy (median 18 Gy). Follow-up periods ranged from 3 months to 98 months (median 23.5 months).


In total, 39 GKS procedures were performed for 28 lesions. The local control rates at 1, 2, and 5 years were 74%, 39%, and 16%, respectively. Volume less than 6 cm3 (p = 0.01), a margin dose higher than 18 Gy (p = 0.02), and a Karnofsky Performance Scale (KPS) score of 90 or more (p = 0.02) were factors associated with a longer duration of tumor control in the univariate analysis.


Atypical meningioma could be more successfully controlled when a higher margin dose was used to treat patients with a good performance (KPS score of ≥ 90) status and smaller tumor volumes. It would be desired if patients are treated with a relatively higher margin dose, ideally as high as the dose applied for malignant tumor. A boost SRS after fractionated radiotherapy may be effective to achieve better local control.

Abbreviations used in this paper:FRT = fractionated radiation therapy; GKS = Gamma Knife surgery; GTR = gross-total resection; KPS = Karnofsky Performance Scale; LC = local control; OS = overall survival; SRS = stereotactic radiosurgery; STR = subtotal resection.

Article Information

Address correspondence to: Shunya Hanakita, M.D., Department of Neurosurgery, University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. email:

Please include this information when citing this paper: published online September 27, 2013; DOI: 10.3171/2013.8.JNS13343.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Patterns of recurrence. A and B: Local failure. The tumor at the cavernous sinus was irradiated at the first GKS. The lesion could not be controlled and expanded to involve the internal carotid artery during the follow-up period. C and D: Marginal recurrence. The recurrent tumor at the convexity region treated by the first GKS was successfully decreased in size. However, at the parasagittal sinus region to which the resected tumor was adjacent, a new tumor developed after 38 months of follow-up. E and F: Distant recurrence. The tumor at the falx region was treated by the initial GKS. After 19 months of follow-up, a new tumor was detected at the convexity region, to which it was not contiguous.

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    A: Kaplan-Meier curves for LC rate with 95% CI. The actuarial LC rate was 74% at 1 year (95% CI 54%–87%), 39% at 2 years (95% CI 17%–55%), and 16% at 5 years (95% CI 4%–44%), according to the Kaplan-Meier method. B–D: Kaplan-Meier curves for LC rates of statistically significant prognostic factors (target volume < 6 cm3 [B], margin dose > 18 Gy [C], and KPS score ≥ 90 [D]).


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