Abstract
Abstract
Objectives
Schwannoma expansion after radiotherapy has not been well-studied despite the clinical importance of distinguishing transient increase from permanent expansion. Thus, this study aimed to identify the underlying mechanism and novel radiological predictors of schwannoma expansion after radiotherapy.
Materials & methods
We retrospectively examined the therapeutic effects of radiotherapy on schwannomas and magnetic resonance images of 43 patients with vestibular schwannomas who underwent stereotactic radiotherapy or radiosurgery at our facility between June 1, 2012 and September 1, 2018. Based on the size change pattern, the treated tumors were classified into six groups, including transient-expansion and consistent-increase groups. The apparent diffusion coefficient (ADC) ratio and appearance of any notch were included as evaluation items based on our hypothesis that transient expansion is due to edema with increased extracellular free water. A log-rank test was performed to evaluate the relationship between the local control rate and radiological signs.
Results
The mean overall 5-year local control rate was 90%, and the median follow-up period was 62 (24–87) months. Approximately 28% of the tumors showed transient expansion; all ADC ratios synchronized with size change, and 75% showed a new notch appearance. Approximately 9% of tumors showed consistent increase, with no notch on the outline. The log-rank test revealed a difference in the local control rate with or without notch appearance in expanding irradiated schwannomas. All tumors with notch appearance showed a significant regression 5 years after radiation.
Conclusions
New notch appearance on the outline could indicate favorable long-term outcomes of expanding schwannomas post-treatment.
Clinical relevance statement
Notch appearance can help differentiate a transient schwannoma from a real tumor expansion, and it is a novel predictor of better outcomes of expanding schwannomas after radiotherapy.
Graphical Abstract
Publisher
Springer Science and Business Media LLC
Reference31 articles.
1. Helbing DL, Schulz A, Morrison H. Pathomechanisms in schwannoma development and progression. Oncogene. 2020;39:5421–9. https://doi.org/10.1038/s41388-020-1374-5.
2. Skolnik AD, Loevner LA, Sampathu DM, Newman JG, Lee JY, Bagley LJ, Learned KO. Cranial nerve schwannomas: diagnostic imaging approach. Radiographics. 2016;36:1463–77. https://doi.org/10.1148/rg.2016150199.
3. Stangerup SE, Caye-Thomasen P, Tos M, Thomsen J. The natural history of vestibular schwannoma. Otol Neurotol. 2006;27:547–52. https://doi.org/10.1097/01.mao.0000217356.73463.e7.
4. Graffeo C. Chapter 6: Disease presentation of sporadic vestibular schwannoma. In: Carlson ML, Link MJ, Driscoll CL, et al. editors. Comprehensive Management of Vestibular Schwannoma. New York; 2019.
5. Hasegawa T, Kida Y, Kato T, Iizuka H, Kuramitsu S, Yamamoto T. Long-term safety and efficacy of stereotactic radiosurgery for vestibular schwannomas: evaluation of 440 patients more than 10 years after treatment with gamma Knife surgery. J Neurosurg. 2013;118:557–65. https://doi.org/10.3171/2012.10.jns12523.