Acoustic neuroma radiosurgery with marginal tumor doses of 12 to 13 Gy.

Abstract

To define tumor control and clinical outcomes of radiosurgery to marginal tumor doses of 12-13 Gy for unilateral acoustic neuroma patients. Three hundred thirteen patients with previously untreated unilateral acoustic neuromas (vestibular schwannomas) underwent gamma knife radiosurgery between February 1991 and February 2001 with marginal tumor doses of 12-13 Gy (median, 13 Gy). Median follow-up was 24 months (maximum, 115 months; 36 patients with > or =60 months). Maximum doses were 20-26 Gy (median, 26 Gy), and treatment volumes were 0.04-21.4 mL (median, 1.1 mL). The actuarial 6-year clinical tumor control rate (no requirement for surgical intervention) for the entire series was 98.6 +/- 1.1%. Two patients required tumor resection; one had a complete resection for solid tumor growth and one required partial resection for an enlarging adjacent subarachnoid cyst. Six-year actuarial rates for preservation of facial nerve function, normal trigeminal nerve function, unchanged hearing level, and useful hearing were 100%, 95.6 +/- 1.8%, 70.3 +/- 5.8%, and 78.6 +/- 5.1%, respectively. The risk of developing trigeminal neuropathy correlated with increasing tumor volume (p = 0.038). Acoustic neuroma radiosurgery with doses of 12-13 Gy provides high rates of tumor control and cranial nerve preservation.