• Neurosurgery · Jun 2023

    The Relevance of Biologically Effective Dose for Hearing Preservation After Stereotactic Radiosurgery for Vestibular Schwannomas: A Retrospective Longitudinal Study.

    • Constantin Tuleasca, Iuliana Toma-Dasu, Sebastien Duroux, Daniele Starnoni, Mercy George, Raphael Maire, Roy Thomas Daniel, David Patin, Luis Schiappacasse, Alexandru Dasu, Mohamed Faouzi, and Marc Levivier.
    • Neurosurgery Service and Gamma Knife Center, Lausanne University Hospital (CHUV), Lausanne, Switzerland.
    • Neurosurgery. 2023 Jun 1; 92 (6): 121612261216-1226.

    BackgroundStereotactic radiosurgery has become a common treatment approach for small-to-medium size vestibular schwannomas.ObjectiveTo evaluate relationship between time (beam-on and treatment) and risk of hearing decline after stereotactic radiosurgery for vestibular schwannomas in patients with Gardner-Robertson (GR) baseline classes I and II.MethodsThis retrospective longitudinal single-center study included 213 patients with GR I and II treated between June 2010 and December 2019. Risk of passing from GR classes I and II (coded 0) to other classes III, IV, and V (coded 1) and the increase in pure tone average (continuous outcome) were evaluated using a mixed-effect regression model. Biologically effective dose (BED) was further assessed for an alpha/beta ratio of 2.47 (Gy 2.47 ).ResultsBinary outcome analysis revealed sex, dose rate, integral dose, time [beam-on time odds ratio 1.03, P = .03, 95% CI 1.00-1.06; treatment time ( P = .02) and BED ( P = .001) as relevant. Fitted multivariable model included the sex, dose rate, and BED. Pure tone average analysis revealed age, integral dose received by tumor, isocenter number, time (beam-on time odds ratio 0.20, P = .001, 95% CI 0.083-0.33) and BED ( P = .005) as relevant.ConclusionOur analysis showed that risk of hearing decline was associated with male sex, higher radiation dose rate (cutoff 2.5 Gy/minute), higher integral dose received by the tumor, higher beam-on time ≥20 minutes, and lower BED. A BED between 55 and 61 was considered as optimal for hearing preservation.Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Congress of Neurological Surgeons.

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