Stereotactic radiosurgery for Koos grade IV vestibular schwannoma: a systematic review and meta-analysis

Stereotactic radiosurgery (SRS) is a well-established treatment option for Koos stage I-III vestibular schwannomas (VS), often used as the first line of treatment or after subtotal resection. However, the optimal treatment for Koos-IV VS remains unclear. Therefore, our study aimed to evaluate the effectiveness of SRS as a primary treatment for large VS classified as Koos-IV.

A systematic search was performed on December 28th, 2022, based on PubMed, Web of Science, and Scopus according to the PRISMA statement. The review was updated on September 7th, 2023. The risk of bias was assessed using the NIH Quality Assessment Tool. The R software (ver. 4.3.2) was used for all quantitative analyses and preparation of the forest plots. Publication bias and sensitivity analysis were performed to evaluate the reliability of the obtained results.

Among 2941 screened records, ten studies (1398 patients) have been included in quantitative synthesis. The overall tumor control rate was 90.7% (95%CI 86.3-94.4). Kaplan-Meier estimates of tumor control at 2, 6, and 10 years were 96.0% (95% CI 92.9-97.6%), 88.8% (95% CI 86.9-89.8%), and 84.5% (95% CI, 81.2-85.8%), respectively. The overall hearing preservation rate was 56.5% (95%CI 37-75.1). Kaplan-Meier estimates of hearing preservation rate at 2, 6, and 10 years were 77.1% (95% CI 67.9-82.5%), 53.5% (95% CI 44.2-58.5%), and 38.1% (95% CI 23.4-40.7%), respectively. The overall facial nerve preservation rate was 100% (95%CI 99.9-100.0). The overall trigeminal neuropathy rate reached 5.7% (95%CI 2.9-9.2). The overall rate of new-onset hydrocephalus was 5.6% (95%CI 3-9). The overall rates of worsening or new-onset tinnitus and vertigo were 6.8% (95%CI 4.2-10.0) and 9.1% (95%CI 2.1-19.6) respectively. No publication bias was detected according to the used methods.

Our systematic review and meta-analysis demonstrated a high overall tumor control rate, excellent facial nerve preservation, and low incidence of new-onset or worsened tinnitus and vertigo. However, several drawbacks associated with SRS should be noted, such as the presence of post-SRS hydrocephalus risk, mediocre long-term hearing preservation, and the lack of immediate tumor decompression. Nevertheless, the use of SRS may be beneficial in appropriately selected cases of Koos-IV VS. Moreover, further prospective studies directly comparing SRS with surgery are necessary to determine the optimal treatment for large VS and verify our results on a higher level of evidence. Registration and protocol: CRD42023389856.