Linear accelerator radiosurgery for vestibular schwannoma

Object. The use of radiosurgery in the treatment of acoustic neuromas has i ncreased substantially during the last decade. Most published experience re lates to the use of the gamma knife. In this report, the authors review the methods and results of linear accelerator (LINAC) radiosurgery in 44 patie nts with acoustic neuromas who were treated between 1993 and 1997. Methods. Computerized tomography scanning was selected as the stereotactic imaging modality for target definition. A single, conformally shaped isocen ter was used in the treatment of 40 patients; two or three isocenters were used in four patients who harbored very irregular tumors. The radiation dos e directed to the tumor border was the only parameter that changed during t he study period in the first 24 patients who were treated the dose was 15 t o 20 Gy, whereas in the last 20 patients the dose was reduced to 11 to 14 G y. After a mean follow-up period of 32 months (range 12-60 months), 98% of the tumors were controlled. The actuarial hearing preservation rate was 71% . New transient facial neuropathy developed in 24% of the patients and pers isted to a mild degree in 8%. Radiation dose correlated significantly with the incidence of cranial neuropathy, particularly in large tumors (greater than or equal to 4 cm(3)). Conclusions. Single-isocenter LINAC radiosurgery proved to be an effective treatment for acoustic neuromas in this series, with results that were comp arable with those reported for gamma knife radiosurgery and multiple isocen ters.