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.
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).
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 ≤) was associated with higher BEDGy2.47 mean at 6 (OR 1.36, P = .002), 12 (OR 1.36, P = .007), and 36 (OR 1.37, P = .02) months. Risk of hearing decline at 36 months for the BEDGy2.47 mean of 7-8, 10, and 12 Gy2.47 was 28%, 57%, and 85%, respectively.
Cochlear BEDGy2.47 mean is relevant for hearing decline after SRS and more relevant as compared with BEDGy2.47 max. Three years after SRS, this was sustained for all hearing decline evaluation modalities. Our data suggest the BEDGy2.47 mean cut-off of ≤8 Gy2.47 for better hearing preservation rates.