Radiation Therapy for the Treatment of Vestibular Schwannoma: A Critical Evaluation of the State of the Literature

Objective: Review publications reporting radiation treatment of vestibular schwannomas (VS) and describe how data, patient characteristics, and study endpoints were reported. Data Sources: PubMed search for English language articles on radiation treatment of VS published from January 2002 to July 2007. Study Selection: Studies presenting outcomes were selected, yielding 56 articles (58 studies) in journals of neurosurgery (30), oncology (18), otolaryngology (6), and other (2). Data Extraction/Synthesis: Data included type of study, number of subjects, demographics, follow-up times, type of radiation, tumor size, tumor control definition, control rates, facial nerve function measure and outcome, type of hearing and vestibular testing and outcomes, and complications. Descriptive statistics were performed. Results: Studies (72.9%) were retrospective reviews with stated sample sizes ranging from 5 to 829. Gamma-knife (49.2%), linear accelerator (35.6%), and proton beam (6.8%) were used with various doses. Average follow-up was less than 5 years in 79.6% of studies, and 67.4% included patients at less than or equal to 1 year. Tumor size was reported as diameter (23.7%), volume (49.2%), both (11.9%), other (3.4%), or not reported (11.9%). Definition of tumor control varied: less than or equal to 2 mm growth (22.0%), no visible/measurable change (16.9%), required surgery (10.2%), other (17.0%), and not clearly specified (33.9%). Facial nerve outcome was reported as House-Brackmann (64.4%), normal/abnormal (11.9%), other (1.7%), or was not reported (22%). Conclusion: The lack of uniform reporting criteria for tumor control, facial function and hearing preservation, and variability in follow-up times make it difficult to compare studies of radiation treatment for VS. We recommend consideration of reporting guidelines such as those used in otology for reporting VS resection results.