Long-Term Outcomes of Gamma Knife Radiosurgery for Cystic Vestibular Schwannomas

Objective: Vestibular schwannomas (VSs) can either be solid or contain variable amounts of cystic components. It has been established that gamma knife radiosurgery (GKRS) is an effective treatment modality for solid VSs. However, in the case of cystic VS, given the somewhat unpredictable growth of the cystic portion of these tumors, microsurgery has often been preferred to GKRS in the management of cystic VS. However, to date, a relative paucity of data evaluating the outcomes after GKRS for cystic VS has been available. In the present study, we reviewed our experience treating cystic VSs with GKRS and evaluated the results. Methods: The data from patients with a diagnosis of cystic VS who had undergone GKRS from 1999 to 2018 were analyzed. Only those patients who had undergone GKRS as the initial treatment of cystic VSs were included in the present study. Patients who had undergone previous surgical treatment were excluded. The cystic VSs were divided into intratumoral and peritumoral cysts. Results: A total of 24 patients were enrolled in the present study. The mean age was 60.8 ± 2.4 years (range, 38–82 years). The mean follow-up period was 55.8 ± 8.1 months (range, 8–145 months). Of the 24 patients, 11 were men. The control rate after GKRS for cystic VSs was 75%. The 5-year progression-free rate was 70%. Six patients had presented with an increasing lesion size after GKS. Of these 6 patients, 2 underwent surgical treatment and 1 underwent repeat GKRS. No statistically significant differences were found between the control rate and cystic type (P = 0.093). Conclusion: The results from the present study have demonstrated that GKRS is an effective treatment modality for cystic VSs.