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Journal of Korean Neurosurgical Society 2007;42(4): 286-292.
doi: https://doi.org/10.3340/jkns.2007.42.4.286
Long-term Outcomes of Gamma Knife Stereotactic Radiosurgery of Vestibular Schwannomas.
Kang Min Kim, Chul Kee Park, Hyun Tai Chung, Sun Ha Paek, Hee Won Jung, Dong Gyu Kim
Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea. gknife@plaza.snu.ac.kr
Gamma Knife Stereotactic Radiosurgery (GK SRS) has become an important treatment modality for vestibular schwannomas. We evaluated the tumor control rate, patterns of tumor volume change and preservation of hearing following low-dose radiation for vestibular schwannomas in a homogeneous cohort group in which the mean marginal dose was 12 Gy.
A total of 59 patients were enrolled in this study. All enrolled patients were followed-up for at least 5 years and the radiation dose was 11-13 Gy. Regular MRI, audiometry and clinical evaluations were done and tumor volumes were obtained from MRI using the OSIRIS program.
The tumor control rate was 97%. We were able to classify the patterns of change in tumor volume into three categories. Transient increases in tumor volume were detected in 29% of the patients and the maximum transient increase in tumor volume was identified at 6 to 30 months after GK SRS. The transient increases in tumor volume ranged from 121% to 188%. Hearing was preserved in 4 of the 12 patients who had serviceable hearing prior to treatment. There were no other complications associated with GK SRS.
Low-dose GK SRS was an effective and safe mode of treatment for vestibular schwannomas in comparison to the previously used high-dose GK SRS. Transient increases in tumor volume can be identified during the follow-up period after low-dose GK SRS for vestibular schwannomas. Physicians should be aware that these increases are not always indicative of treatment failure and that close observation is required following treatments. Unfortunately, a satisfactory hearing preservation rate was not achieved by reducing the radiation dose. It is thought that hearing preservation is a more sophisticated problem and further research is required.
Key Words: Vestibular schwannomas; Gamma knife; Low dose; Long-term outcome
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