2150 - Cochlear Dose as a Predictor of Hearing Preservation in Patients with Vestibular Schwannoma Treated with Fractionated Stereotactic Radiotherapy
Presenter(s)
L. N. McLean1, R. Hernandez2, G. O'Neill3, G. Hernandez2, A. Chhabra2, Y. Qu2, A. Haendel-Gonzalez2, J. Evans4, C. Farrell4, D. W. Andrews4, and W. Shi5; 1Dept. of Radiation Oncology, Sidney Kimmel Medical College and Comprehensive Cancer Center, Thomas Jefferson University, Philadelphia, PA, 2Sidney Kimmel Medical College and Comprehensive Cancer Center, Thomas Jefferson University, Philadelphia, PA, 3Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, 4Department of Neurosurgery, Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, 5Department of Radiation Oncology, Sidney Kimmel Medical College & Cancer Center at Thomas Jefferson University, Philadelphia, PA
Purpose/Objective(s):
Although stereotactic radiotherapy (SRT) for vestibular schwannoma achieves excellent local control, post-treatment hearing deterioration remains a significant concern. We conducted an audiometry-based analysis to evaluate the impact of cochlear radiation dosimetry and baseline patient characteristics on hearing preservation following fractionated SRT in patients with vestibular schwannoma.Materials/Methods:
This is a single-institution retrospective study of patients with vestibular schwannoma who received SRT. Audiometric and dosimetric data were collected retrospectively. Pure tone average (PTA) and word recognition score (WRS) at baseline and follow-up were used to calculate short-term (3–6 months) and long-term (12–36 months) changes. Cochlear doses were recorded, with comparisons at the 36 Gy threshold. Baseline hearing status was evaluated to compare the magnitude of decline at short-term and long-term follow-up between patients with Grade 1 hearing (defined as PTA 0-30 dB with WRS 70-100%) versus Grade 2 hearing (defined as PTA 31-50 dB with WRS 50-69%). The change in Statistical analysis included two-tailed and non-parametric tests to account for non-normal distributions.Results:
A total of 63 patients were included in this study. The median short-term decline in PTA was 12.0 dB (10 to 57 dB), while the median long-term decline in PTA was 16.5 dB (12 to 46 dB). Conversely, the median short-term decline in WRS was –4 % points (-100 to -36%), and the median long-term decline in WRS was –20 % points (-76 to 34%). Patients with cochlear mean dose = 36 Gy had significantly worse early WRS decline (-16 vs. -4 points, ss). When comparing baseline hearing status, GR2 patients experienced ~10% more long-term WRS loss than those in GR1 (–38% vs. –28%). PTA decline remained relatively consistent across both groups (short-term: 15 dB in both GR1 and GR2; long-term: 15.5 dB in GR1 vs 22 dB in GR2). Notably, long-term hearing preservation was 50% in patients receiving <36 Gy compared with 37.5% in those receiving =36 Gy (p<0.05). Short-term hearing preservation similarly favored lower cochlear doses, with 61.5% preservation at <36 Gy vs 35.3% at=36 Gy (p<0.05). Patients with GR1 baseline hearing had significantly better long-term hearing preservation than patients with GR2 hearing (88% vs 29%, respectively; p<0.05).Conclusion:
In this study, cochlear radiation dose was an independent predictor of hearing preservation. A cochlear mean dose <36 Gy was associated with better hearing outcomes. Patients with baseline Gardner–Robertson class II hearing experienced greater deterioration than those with class I. Larger studies with long-term audiometric follow-up are needed to confirm the impact of cochlear dose on hearing preservation.