Large vestibular schwannoma treated using a cranial nerve sparing approach with planned subtotal microsurgical resection and stereotactic radiosurgery: meta-analysis and International Stereotactic Radiosurgery Society (ISRS) practice guidelines

Introduction: Stereotactic radiosurgery (SRS) has become a standard of care for small- to medium- size vestibular schwannomas (VS), while the majority of patients with large VS still require microsurgical resection due to potential consequences of long tract and cranial nerve compression, intracranial hypertension or hydrocephalus. Methods: We performed a systematic review and meta-analysis of the literature specific to planned subtotal resection for large VSs followed by SRS to the residual tumor to inform clinical practice guideline development. The Medline and Embase databases were used to apply the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) approach to search for manuscripts reporting outcomes for large VSs treated with this paradigm, with a search end date of June 1st 2023. Crude outcomes were pooled using weighted random effects. Results: 12 series met inclusion criteria reporting on treatment outcomes for 677 patients. Overall tumor control was 89.9% (86.9–92.9%, p < 0.001), with tumor stability observed in 43.9% (19.9–68%, p < 0.001) and tumor reduction in 39.9% (57–74.2%, p = 0.02) post-SRS. Facial nerve functional preservation immediately after microsurgery was 88.0% (82.7–93.3%, p < 0.001), improving to 94.4% (91.4–97.4%, p < 0.001) at last follow-up. Cochlear functional preservation immediately after microsurgery was 58.8% (33.2–84.4%, p < 0.001), decreasing to 57.4% (33–81.8%, p < 0.001) at last follow-up. Conclusions: A cranial nerve sparing approach with planned subtotal microsurgical resection and SRS to the residual tumor achieves high rates of tumor control with highly satisfactory outcome of facial and cochlear functional preservation. Clinical practice consensus recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS) are also presented.