Clinical and Radiologic Results from the Long-Term Follow-Up of More than 10 Years in Patients Undergoing Gamma Knife Radiosurgery for Vestibular Schwannoma

Corresponding author: Do Hoon Kwon Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Republic of Korea Tel: +82-2-3010-3550 Fax: +82-2-476-6738 E-mail: dhkwonasan@gmail.com Objective: Vestibular schwannoma (VS) is a benign, slow-growing tumor originating from Schwann cells of the cranial nerve. Many studies have reported short-term follow-ups of patients with VS undergoing gamma knife radiosurgery (GKR). This study analyzed factors affecting the treatment and prognosis of patients over a 10-year period who underwent GKR at a single center by 1 surgeon. Methods: Between 1990 and 2003, we used GKR as a primary treatment or after prior surgical tumor removal for patients with VS. During this period, a single surgeon in 1 center treated more than 700 patients. Of these, 182 patients available for long-term follow-up via the outpatient department were included in the study. Among them, 156 patients were available for radiological imaging follow-up; patients who were not available for radiological follow-up were excluded. Initial tumor volume, initial prescription dose, prior surgery, neurological symptom improvement, and tumor control by individual status were assessed to analyze the factors associated with treatment outcomes. Results: Analysis revealed that a smaller initial volume led to better outcomes of tumor control. Conclusion: At more than 10years’ follow-up, GKR for VS was effective for tumor control in 91.0% of cases and there were few complications associated with GKR. With improvements in the technology and precision of gamma knife systems, planning programs, and other treatment protocols such as fraction and low marginal dose, we should continuously study following results. Our study results suggest the need for more effective methods for tumor control and fewer neurological and GKR-associated complications.