Tumor Shrinkage Of Vestibular Schwannomas Treated With Gamma Knife Surgery: Results Of More Than 5 Years Follow-up

Osamu Nagano1, Toru Serizawa2, Yoshinori Higuchi3, Shinji Matsuda4, Makoto Sato4, Kouichi Okiyama5, Junichi Ono6, Naokatsu Saeki5

1Ichihara, Japan 2Tokyo, Japan 3Chiba, Japan 4Gamma Knife House 5 Departments of Neurological Surgery 6 Departments of Neurosurgery

Keywords: gamma knife, radiosurgery, vestibular schwannoma, outcome, brain tumor

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     To review tumor shrinkage after gamma knife surgery (GKS) for vestibular schwannomas (VSs).
     Among 186 VS treated with GKS, 87 consecutive unilateral VS observed on follow-up MRI for at least 5 years were analyzed.
     For each lesion the Gadolinium enhanced volume was measured serially every 3 months for 2 years and 6-12 months thereafter using GammaPlanTM or SurgiPlanTM. The frequency and degree of volume shrinkage were documented.
     There were 31 men and 56 women, with a mean age of 58.8, range 29 to 80, years. The tumor volume at GKS averaged 2.5 cc (0.1 -13.2 cc), and was irradiated with 50 (50-67) % 12 (10.5-13.0) Gy at the periphery. The mean observation period was 6.4 years (5.0-10.5). Peak volume expansion was most frequently observed at 6.4 post-GKS months and averaged 58% (0-613%). The mean volume shrinkage was 31% and 11 tumors were still larger than the initial volume at 5 years after GKS. The homogeneous enhanced tumors were related to less shrinkage.
     This is a retrospective study.
      MRI findings correlated with tumor shrinkage.
     Most VS showed shrinkage at 5 years after GKS. The mean volume shrinkage was 31%.


Project Roles:

O. Nagano (), T. Serizawa (), Y. Higuchi (), S. Matsuda (), M. Sato (), K. Okiyama (), J. Ono (), N. Saeki ()