Outcomes of stereotactic radiosurgery for large vestibular schwannomas: a systematic review and meta-analysis

Background. Large vestibular schwannomas (VS) pose a treatment challenge for both microsurgery (MS} and stereotactic radiosurgery (SRS). Technical developments have allowed for safer irradiation of large tumors. It remains unclear if SRS can achieve appropriate tumor control and acceptable cranial nerve toxicities. In this study, we asess outcomes of irradiation for large VS. Methods. PubMed MEDLINE, EIVIBASE, Web of Science, and Cochrane were searched for all the studies assessing RS outcome n large VS. Primary endpoints included clinical and radiographic tumor control, need far salvage s urgery, serviceable hearing, cranial nerve V and VII impairment, presence of hydrocephalus requiring shunting, and presence of vertigo/dizziness. Results. Twenty-two studies were identified that met selection criteria for analysis from an initial pool of 1272 reports. They were evaluated according to treatment protocol: 1) single-dose SRS (13 studies, 483 patients), 2) combination of MS and SRS (7 studies, 182 patients), and 3) fractionated SRS (3 studies, 82 patients). Tumor control was achieved in 89%, 94%, and 91% of patients, respectively. Odds ratios (ORs) of post- over pretreatment serviceable hearing were 0.42 (P < .01), 0.47 (P = .05), and 0.60 (P = .22); for facial nerve impairment, these ORs were 1.08 (P = .69), 3.45 (P = .28), and 0.87 (P = .71), respectively. Conclusions. The management of large VS remains challenging. All treatment modalities resulted in high tumor control rates and worsening of pretreatment hearing. None, however, caused significant facial nerve impairment, suggesting that management strategies incorporating focal irradiation can be successful.