Large Vestibular Schwannomas

Single-fraction radiosurgery has demonstrated its efficacy in large and very large series of patients with vestibular schwannomas. However, single-fraction radiosurgery is reserved to small- to medium-sized lesions. The current standard therapeutic dose (12\u201314 Gy) may actually be too high to be tolerated by healthy surrounding nerve structures, such as the brainstem, which are in direct contact with large schwannomas. Furthermore, there is a direct correlation between tumor size and facial nerve damage. Hypofractionated treatments can be adopted in larger lesions when the patient is not a candidate for surgical resection. The lower dose per fraction used in hypofractionated schedules is, in theory, less harmful for the surrounding healthy structures allowing for higher rates of hearing, facial, and trigeminal nerve preservation, especially in such large lesions. Despite the limited experience in the treatment of Koos grade IV vestibular schwannomas, the results appear interesting, with local tumor control at midterm that are not very different from those obtained in smaller tumors. The major complication is represented by a form of subacute hydrocephalus that affects 10\u201315% of patients that become symptomatic in weeks and can be treated without the necessity of tumor resection. Although controversial, a similar approach represents a valid and effective treatment modality at least for elderly patients or for those with severe medical comorbidities, for whom radiosurgery can be a treatment option. Here, we review the role of hypofraction for the treatment of large and very large vestibular schwannomas and provide practical suggestions for its application

CyberKnife for Treatment of Vestibular Schwannoma: A Meta-analysis

Objectives (1) Perform a meta-analysis of the available data on the outcomes of CyberKnife radiosurgery for treatment of vestibular schwannomas (VSs) in the published English-language literature and (2) evaluate the collective outcomes of CyberKnife treatment with respect to tumor control and hearing preservation. Data Sources A thorough literature search of published English-language articles was performed in the PubMed, Ovid, and Cochrane databases. Review Methods A database search was conducted with the keywords "CyberKnife" and "vestibular schwannoma" or "acoustic neuroma." A total of 25 papers were found and reviewed. Data were extracted for patient demographics, number of patients with neurofibromatosis type 2, pretreatment hearing status, tumor size, margin dose, and follow-up duration. The primary outcome variables evaluated were tumor control and hearing preservation. Results After careful review of the published articles, 11 papers reported data on outcomes of CyberKnife treatment for VS and were included in the analysis, comprising 800 patients studied during 1998 to 2012. The reported mean tumor volume ranged from 0.02 to 19.8 cm3, and the follow-up duration ranged from 6 to 120 months. Margin dose varied from 14 to 25 Gy. The collective mean tumor control rate was 96.3% (95% CI: 94.0%-98.5%). The collective hearing preservation rate was 79.1% (95% CI: 71.0%-87.3%) in 427 patients with measurable hearing. Conclusion Clinical data on outcomes of CyberKnife radiosurgery for treatment of VSs are sparse and primarily limited to single-institution analyses, with considerable variation in tumor volume and follow-up time. This meta-analysis not only provides an in-depth analysis of available data in the literature but also reviews reported outcomes and complications