Stereotactic radiosurgery using the gamma knife for XXXX .

@entity1 @entity5513 @entity137 @entity5 @entity16 @entity425
PURPOSE: To assess the efficacy and @entity137 of stereotactic radiosurgery using the gamma knife for @entity5513 . METHODS AND MATERIALS: Between January 1990 and January 1993, 36 @entity1 with @entity5513 were treated with stereotactic radiosurgery using the gamma knife. The median maximum @entity5 diameter was 21 mm (range: 6-32 mm). @entity5 volumes encompassed within the prescribed isodose line varied from 266 to 8,667 mm3 (median: 3,135 mm3). @entity5 < or = 20 mm in maximum diameter received a dose of 20 Gy to the margin, @entity5 between 21 and 30 mm received 18 Gy, and @entity5 > 30 mm received 16 Gy. The dose was prescribed to the 50% isodose line in 31 @entity1 and to the 45%, 55%, 60%, 70%, and 80% isodose line in one @entity1 each. The median number of isocenters per @entity5 was 5 (range: 1-12). RESULTS: At a median follow-up of 16 months (range: 2.5-36 months), all @entity1 were alive. Thirty-five @entity1 had follow-up imaging studies. Nine @entity5 (26%) were smaller, and 26 @entity5 (74%) were unchanged. No @entity5 had progressed. The 1- and 2-year actuarial incidences of @entity16 were 52.2% and 66.5%, respectively. The 1- and 2-year actuarial incidences of @entity16 were 33.7% and 58.9%, respectively. The 1- and 2-year actuarial incidence of @entity16 (or both) was 60.8% and 81.7%, respectively. Multivariate analysis revealed that the following were associated with the time of onset or worsening of @entity425 or @entity16 : (a) @entity1 < age 65 years, (b) dose to the @entity5 margin, (c) maximum @entity5 diameter > or = 21 mm, (d) use of the 18 mm collimator, and (e) use of > five isocenters. The 1- and 2-year actuarial rates of preservation of useful hearing (Gardner-Robertson class I or II) were 100% and 41.7% +/- 17.3, respectively. CONCLUSION: Stereotactic radiosurgery using the gamma knife provides short-term control of @entity5513 when a dose of 16 to 20 Gy to the @entity5 margin is used. Preservation of useful hearing can be accomplished in a significant proportion of @entity1 .
