Tumor Shrinkage Of Vestibular Schwannomas Treated With Gamma Knife Surgery: Results Of More Than 5 Years Follow-upOsamu Nagano1, Toru Serizawa2, Yoshinori Higuchi3, Shinji Matsuda4, Makoto Sato4, Kouichi Okiyama5, Junichi Ono6, Naokatsu Saeki51Ichihara, 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
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 ()