Stereotactic Radiosurgery as Primary Treatment in Fast-Growing Vestibular Schwannomas: A Meta-analysis

Introduction: Approximately 10% of intracranial tumors are vestibular schwannomas with controversy still surrounding their optimal treatment. Stereotactic radiosurgery (SRS) is increasingly utilized for small and medium sized tumors. However, the effect of pretreatment growth rate on the efficacy of SRS remains unknown. This review aimed to establish the impact of the pre- treatment tumor growth rate on the efficacy of SRS in patients with sporadic, growing VS. A secondary aim was to assess severe side effects of treatment in this group of patients.

Methods: A literature search of MEDLINE and EMBASE was performed. 92 publications met the inclusion/exclusion criteria. Articles were assessed by two authors independently and the resulting four articles found to be suitable were critically appraised. Data from selected studies were reviewed and extracted by the third author independently. These were analyzed using R version 3.6.2 (2019–12–12), R-Studio v1.2c with the Metafor package. Based on the selected studies, which were case series observational, a meta-analysis with the random-effect model for the odds of success was performed. Success in the meta-analysis was defined as static tumor size or decreasing size following treatment.

Results: From the four studies, there were a total of 487 patients. The size of the treated tumors varied widely (range: 0.04–12.18 cm³) as did the pre- and posttreatment follow-up period (range: 12–159 months, and 5.1–85.1 months, respectively). A significant amount of variability was identified in both the study definitions and study design. This made statistical analysis difficult. However, it appears that faster growing tumors have lower success rates with SRS treatment. Side effects were documented in most of the studies but were of limited statistical analysis and interpretation.

Discussion: The heterogeneity of the studies made direct comparisons problematic. None of the studies had a comparative arm; therefore, true effect size could not be established. Prospective studies with standardized methods of reporting growth rates and response to treatment are required to better assess the exact success rates of SRS in controlling fast growing VS. Despite this, our review does indicate that faster growing tumors are less radiosensitive with higher failure rates. Side effects of SRS were minimal.

Conclusion: Although our results need to be taken with caution, the fact that faster growing tumors appear to be less sensitive to SRS may assist in patient counseling and treatment decision making.

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Artikel online veröffentlicht:
12. Februar 2021