Presenter(s)
S. Shrivastava1, S. Neerumalla2, R. Whitehead2, E. Michaelides2, and K. Tatebe3; 1Rush Medical College of Rush University, Chicago, IL, United States, 2Rush Medical College, Chicago, IL, 3Rush University Medical Center, Chicago, IL
Purpose/Objective(s): Stereotactic radiosurgery (SRS) is a cornerstone of vestibular schwannoma treatment, yet radiation-induced cochlear injury remains a major cause of hearing decline. Current planning relies on mean cochlear dose, a global metric that does not fully address the cochlea’s tonotopic organization. We evaluated whether radiation dose to frequency-specific cochlear regions independently predicts post-treatment hearing thresholds after accounting for baseline hearing and inter-patient confounders.
Materials/Methods: Seventeen patients with pre- and post-treatment audiometry contributed 102 tonotopic observations (six frequencies per patient). For each frequency, the corresponding regional cochlear dose was extracted. Post-treatment thresholds were modeled using (1) pooled regression, (2) patient fixed-effects models accounting for within-patient comparisons, and (3) models allowing the effect of dose to vary with baseline hearing.
Results: Baseline hearing strongly predicted post-treatment thresholds (r = 0.69). In pooled regression, dose showed a statistically significant negative association with post-treatment threshold (-0.021 dB/cGy; p = 0.0005), a paradoxical effect resulting from between-patient confounding. After incorporating patient-specific intercepts and adjusting for baseline hearing, local cochlear dose showed a positive association with greater hearing loss: 5.9 dB/Gy (95% CI -0.90 to 12.72). Models allowing for varying sensitivity demonstrated that the dose–response becomes stronger with poorer baseline hearing: approximately 3.16 dB/Gy at 20 dB HL, 4.41 dB/Gy at 40 dB HL, 5.65 dB/Gy at 60 dB HL, and 6.90 dB/Gy at 80 dB HL.
Conclusion: Tonotopic analyses that do not adjust for patient-level heterogeneity may obscure the true cochlear dose–response relationship. After appropriate adjustment, higher radiation dose to specific cochlear regions appears associated with greater hearing loss, with this effect increasing with worsening baseline hearing thresholds. These results may inform future cochlear sparing strategies to better preserve functional hearing.