Gamma Knife Radiosurgery for Vestibular Schwannomas: Identification of Predictors for Continued Tumor Growth and the Influence of Documented Tumor Growth Preceding Radiation Treatment

Ferdinand C. A. Timmer*, Jef J. S. Mulder, Patrick E J Hanssens, J. J. van Overbeeke, Rogier T. Donders, Cor W. R. J. Cremers, Kees Graamans

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Gamma knife radiosurgery (GKRS) has become an important treatment modality for vestibular schwannomas. The primary aim of this study was to investigate whether tumor growth at the moment of GKRS has any correlation with the outcome. The secondary aim was to identify clinical predictors of radioresistance in vestibular schwannoma patients treated with GKRS.One hundred vestibular schwannoma patients, treated with GKRS, were divided into two groups: 1) proven tumor growth preceding GKRS; and 2) previous history of growth unknown. GKRS outcome was defined in two ways. According to the first definition, GKRS was said to have failed when additional treatment had taken place. According to the second one, a volume decrease >20% after 2 years marked successful treatment.Correlations between outcome and growth status were determined with SPSS software. Furthermore, the study assessed how different variables (patient data, history, tumor characteristics, imaging, and audiovestibular examinations) correlated with the outcome of GKRS.No significant difference regarding success and failure of GKRS was found between the two patient groups. The mean reduction in tumor volume after GKRS was less pronounced in patients in whom tumor growth was demonstrated before treatment, but this finding was not significant. No significant predictors (P <.05) could be identified in this data set.This study found no indication that growth at the moment of GKRS influences therapeutic outcome, nor did it identify any predictors of the outcome after GKRS in vestibular schwannoma patients. The American Laryngological, Rhinological, and Otological Society, Inc.
Original languageEnglish
Pages (from-to)1834-1838
Issue number9
Publication statusPublished - Sept 2011


  • Acoustic neuroma
  • vestibular schwannoma
  • gamma knife
  • growth prediction

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