Hearing Preservation in Vestibular Schwannoma after Radiosurgery: A Meta-Analysis

Introduction: There is a wide range of reported hearing preservation rates in patients with vestibular schwannoma (VS) undergoing gamma knife radiosurgery (GKRS). Hearing outcomes following GKRS are multifactorial and poorly characterized in prior literature. The focus of this study was the characterization of hearing outcomes and identification of the prognostic factors of serviceable hearing preservation rates following GKRS for VS.

Materials and Methods: Six medical databases were queried according to PRISMA guidelines. Inclusion criteria was as follows: (1) VS was the sole tumor target, (2) single-fraction GKRS was the only form of radiosurgery used as therapy, and (3) hearing preservation rate was reported following GKRS. Studies with ≥10% of cases with prior treatment or ≥10% of patients with neurofibromatosis type II were excluded. A meta-analysis was performed for all variables of interest and a random-effect model was utilized to account for interstudy heterogeneity. All data were analyzed using Stata 17 SE software. Hearing preservation was defined as a postoperative Gardner-Robertson (GR) score of ≤ II among patients with preoperative serviceable hearing.

Results: Data of interest was available for 42 articles with 6,582 patients with an average age of 54.4 years. Age ≥55 years and tumor volume >2.5 cm³ were found to be independently associated with a worse preoperative hearing status relative to age <55 years (GR I: p = 0.002, GR I or II: p = 0.0001) and tumor size <2.5 cm³ (GR I: p = 0.03, GR I or II: p = 0.005). The pooled proportion of preoperative serviceable hearing was 75.3%, which decreased postoperatively to 42.3% at the last follow-up visit. Pooled postoperative hearing preservation rates at the 3-, 5-, and 10-year follow-up periods were 72.8, 63.2, and 35.5%, respectively. Age ≥55 years was significantly associated with reduced hearing preservation rates postoperatively (31.6%) relative to age <55 years (55.8%, p = 0.001, [Fig. 1]). Tumor volume <1.5 cm³ had significantly improved hearing preservation (53.4%) compared to volume >1.5 cm³ (36.8%, p = 0.045, [Fig. 2]). No significant correlation was seen between radiation dose and hearing preservation at the last follow-up visit. However, at a follow-up of 10 years, marginal radiation dose ≤12.5 Gy showed significantly higher rates of serviceable hearing (60.2%) relative to dose >12.5 Gy (20.8%, p = 0.039). The pooled tumor control rate was 95.5% at an average maximum follow-up period of 57.2 months. The most prevalent complications following GKRS were asymptomatic hydrocephalus (2.3%), new trigeminal neuropathy (2.3%), and hydrocephalus requiring shunt placement (1.8%). Repeat GKRS was performed in 1.3% of patients due to tumor progression.

Conclusion: Our comprehensive analysis of 6,582 patients offers an up-to-date, systematic characterization of hearing preservation following GKRS for VS. This study identifies age, tumor volume, and radiation dose as independent prognostic factors for hearing preservation. In patients with VS, overall hearing preservation rates following GKRS may be expected to be approximately 73, 63, and 36% at 3, 5, and 10 years, respectively. This meta-analysis offers an objective overview of the literature with applications in treatment planning, advising patients regarding expected hearing outcomes, and in consideration of channels for the refinement of VS management.

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Artikel online veröffentlicht:
05. Februar 2024