Background: Cochlear dose has been identified as a potentially modifiable contributor to hearing loss following stereotactic radiosurgery (SRS) for vestibular schwannoma (VS).
Objective: (1) to evaluate the association between CT-based volumetric cochlea dose and loss of serviceable hearing following SRS; 2) to assess intra- and interobserver reliability when determining modiolar point dose using MRI and CT; 3) and to discuss the clinical significance of the cochlea dose with regard to radiosurgical planning strategy.
Methods: Patients with serviceable pre-treatment hearing who underwent SRS for sporadic VS between using Gamma Knife Perfexion were studied. Univariate and multivariate associations with the primary outcome of time to non-serviceable hearing were evaluated.
Results: A total of 105 patients underwent SRS for VS during the study period, and 59 (56%) met study criteria and were analyzed. Twenty-one subjects (36%) developed non-serviceable hearing at a mean of 2.2 years following SRS (SD 1.0; median 2.1; range 0.6-3.8). On univariate analysis, pre-treatment pure tone average, speech discrimination score, AAO-HNS hearing class, marginal dose and mean dose to the cochlear volume were statistically significantly associated with time to non-serviceable hearing. However, after adjusting for baseline differences, only pre-treatment PTA was statistically significantly associated with time to non-serviceable hearing using a multivariable model.
Conclusion: Cochlear dose is one of many variables associated with hearing preservation following SRS for VS. Until further studies demonstrate durable tumor arrest with reduced dose protocols, routine tumor dose planning should not be modified to limit cochlear dose at the expense of tumor control.
From: Significance of Cochlear Dose in the Radiosurgical Treatment of Vestibular Schwannoma: Controversies and Unanswered Questions by Jacob et al.