Results of acoustic neuroma radiosurgery: an analysis of 5 years' experience using current methods

Object. The goal of this study was to define tumor control and complication s of radiosurgery encountered using current treatment methods for the initi al management of patients with unilateral acoustic neuroma. Methods. One hundred ninety patients with previously untreated unilateral a coustic neuromas (vestibular schwannomas) underwent gamma knife radiosurger y between 1992 and 1997. The median follow-up period in these patients was 30 months (maximum 85 months). The marginal radiation doses were 11 to 18 G y (median 13 Gy),the maximum doses were 22 to 36 Gy (median 26 Gy), and the treatment volumes were 0.1 to 33 cm(3) (median 2.7 cm(3)). The actuarial 5-year clinical tumor-control rate (no requirement for surgic al intervention) for the entire series was 97.1 +/- 1.9%. Five-year actuari al rates for any new facial weakness, facial numbness, hearing-level preser vation, and preservation of testable speech discrimination were 1.1 +/- 0.8 %, 2.6 +/- 1.2%, 71 +/- 4.7%, and 91 +/- 2.6%, respective ly. Facial weakne ss did not develop in any patient who received a marginal dose of less than 15 Gy (163 patients). Hearing levels improved in 10 (7%) of 141 patients w ho exhibited decreased hearing (Gardner-Robertson Classes II-V) before unde rgoing radiosurgery. According to multivariate analysis, increasing margina l dose correlated with increased development of facial weakness (p = 0.0342 ) and decreased preservation of testable speech discrimination (p = 0.0122) . Conclusions. Radiosurgery for acoustic neuroma performed using current proc edures is associated with a continued high rate of tumor control and lower rates of posttreatment morbidity than those published in earlier reports.