Impact of the Mean Cochlear Biologically Effective Dose on Hearing Preservation After Stereotactic Radiosurgery for Vestibular Schwannoma: A Retrospective Longitudinal Analysis

BACKGROUND AND OBJECTIVES: Stereotactic radiosurgery (SRS) is a useful alternative for small- to medium-sized vestibular schwannoma. To evaluate whether biologically effective dose (BEDGy2.47), calculated for mean (BEDGy2.47 mean) and maximal (BEDGy2.47 max) cochlear dose, is relevant for hearing preservation. METHODS: This is a retrospective longitudinal single -center study. Were analyzed 213 patients with useful baseline hearing. Risk of hearing decline was assessed for Gardner-Robertson classes and pure tone average (PTA) loss. The mean follow-up period was 39 months (median 36, 6-84). RESULTS: Hearing decline (Gardner-Robertson class) 3 years after SRS was associated with higher cochlear BEDGy2.47 mean (odds ratio [OR] 1.39, P= .009). Moreover, BEDGy2.47 mean was more relevant as compared with BEDGy2.47 max (OR 1.13, P= .04). Risk of PTA loss (continuous outcome, follow-up minus baseline) was significantly corelated with BEDGy2.47 mean at 24 (beta coefficient 1.55, P = .002) and 36 (beta coefficient 2.01, P = .004) months after SRS. Risk of PTA loss (>20 dB vs