Radiation dose calculations could protect hearing after brain tumor surgery

<p>BACKGROUND: </p><p>Stereotactic radiosurgery has become a common treatment approach for small-to-medium size vestibular schwannomas.</p><p>OBJECTIVE: </p><p>To 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.</p><p>METHODS: </p><p>This 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).</p><p>RESULTS: </p><p>Binary outcome analysis revealed sex, dose rate, integral dose, time [beam-on time odds ratio 1.03, <em>P</em> = .03, 95% CI 1.00-1.06; treatment time (<em>P</em> = .02) and BED (<em>P</em> = .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, <em>P</em> = .001, 95% CI 0.083-0.33) and BED (<em>P</em> = .005) as relevant.</p><p>CONCLUSION: </p><p>Our 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.</p>