Efficacy of irradiation for incompletely excised acoustic neurilemomas

The records of 124 patients treated for acoustic neurilemoma at the University of California, San Francisco, from 1945 through 1983 were reviewed. Patients were classified by the extent of surgical resection: total, nearly total (90% to 99% resection), subtotal (less than 90% resection), or biopsy. Thirty-one patients received irradiation as part of their primary treatment. Total resection of tumor, without irradiation, was associated with a 3% chance of local recurrence. One of 15 patients who had nearly total resection of their tumor and did not receive postoperative irradiation suffered a recurrence, compared with neither of the two patients who received postoperative irradiation (greater than 45 Gy) following nearly total resection. Postoperative irradiation (greater than 45 Gy) decreased the recurrence rate after subtotal resection from 46% (six of 13 cases without irradiation) to 6% (one of 17 cases: p = 0.01). All three patients treated by biopsy alone received postoperative irradiation (greater than 45 Gy), and none had a recurrence. Six patients were treated with preoperative irradiation because of excessive tumor vascularity; four are without evidence of disease 12 to 23 years later. Only three of seven patients treated with irradiation for tumor recurrence after surgical resection survived. It is concluded that postoperative irradiation significantly decreased the chance for local tumor progression following subtotal resection of acoustic neurilemoma, and that postoperative irradiation may be effective therapy following treatment by biopsy. Patients with total or nearly total resection appeared not to benefit from postoperative irradiation.