Efficacy and safety of multisession gamma knife surgery for benign orbital tumor

Keywords: gamma knife, radiosurgery, meningioma, orbit, vision

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     Techniques, patient selection, and dose-selection remain important issues in the management of orbital tumors.
The goal of this study was to investigate safety and efficacy of multisession gamma knife radiosurgery (GKS) for benign orbital tumors.
     Thirty patients with benign orbital tumors (14 meningiomas, 10 cavernous hemangiomas, 4 schwannomas, 1solitary fibrous tumor and 1 granular cell tumor) were treated with GKS. Among them twenty-four patients with remained vision and tumors touching the optic nerve were treated with multisession (3 or 4 fractions) radiosurgery.
      The mean tumor volume was 3,506 mm3 (211–10,800). Median cumulative marginal dose was 20Gy (15–22) in multisession radiosurgery.
     After a mean follow-up of 25 months (range, 5–74 months), tumor control was confirmed in 22 out of 24 patients. In particular, cavernous hemangioma group(n=7) showed high tumor shrinkage rate (mean 53.7%, range 21.7~90%) during follow up periods (mean 23 months, range 13-38). Of the 24 patients whose preoperative vision was preserved, 12 patients showed improvement in visual acuity and/or visual field, and 12 patients showed stable visual acuity. No adverse events were noted during and after the GKS. None of the patients experienced radiation related morbidity.
     This was a retrospective study.
     GKS provides an effective management strategy in patients with benign orbital tumors. Besides classical single session radiosurgery multisession radiosurgery using Gamma knife may be a good strategy for tumors in direct contact with optic nerve. 
     Up to 20 Gy of cumulative marginal dose in 4 sessions is safe for preservation of visual function with high probability of tumor control.


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