Background: The effectiveness of Diffusion Tensor Imaging (DTI) in demonstrating
functional changes in the tumor in determining the response to treatment after radiosurgery in patients
with vestibular schwannoma (VS) is not clear yet.
Objective: The study aimed to determine the change in total tumor volume (TTV) in terms of radiological
response in patients who had VS and were treated with radiosurgery and investigated the relationship
between the TTV, follow-up times and DTI parameters.
Methods: Thirty-one patients were assessed using DTI and MRI. TTV, apparent diffusion coefficient
(ADC), and fractional anisotropy (FA) were calculated. Patients were divided into three
groups: those who responded to the treatment (group 1) (n=11), those who did not (group 0) (n=9)
and those who remained stable (group 2) (n=11).
Results: The mean duration of follow-up was 28.81±14 months. ADC values increased in patients
with VS after radiosurgery (p=0.004). There was no statistical difference in the FA values. A significant
reduction in TTV after radiosurgery was detected in group 1 (p=0.003). ADC values increased
significantly after radiosurgery in group 2 (p=0.04). Although there were no significant differences,
ADC values after radiosurgery increased in group 1 and group 0.
Conclusions: ADC values continuously increase due to radiation damage in the period before the
tumor volume shrinks after radiosurgery. We think that it is not appropriate to diagnose inadequate
treatment or progression only when TTV is evaluated in terms of response to treatment in the early
period after radiosurgery.