Evaluation of Vestibular Schwannoma Size across Time: How Well Do the Experts Perform and What Can Be Improved?

2D linear measurements are often used in routine clinical practice during vestibular schwannoma (VS) follow-up, primarily due to wider availability and ease of use. We sought to determine the radiologist's performance compared with 3D-volumetry, along with the impact of the number of linear measurements, slice thickness, and tumor volumes on these parameters.

Specificity and accuracy estimates and 95% confidence intervals were calculated for the entire cohort and subgroups on the basis of volumes (<400, 400-800, >800 mm³), slice thickness (≤1.5 mm or >1.5 mm), and number of linear dimensions measured in the radiology report (0-1 or 2-3).

There was weak agreement between the radiologist's inference and VS volumetry (0.45; 95% CI. 0.41-00.53). Agreement was lower when 0-1 tumor dimension was measured (0.29; 95% CI, 0.21-0.42), for smaller tumors of <400 mm³ (0.37; 95% CI, 0.28-0.45), and for thick-section imaging of >1.5 mm (0.36; 95% CI, 0.25-0.46). The reader sensitivity was modest (0.49-0.54), while the accuracy for detecting ≤ ±25% interval change was weak (0.32-0.38). Reader performance trended toward improvement with thin-section imaging, measurement of 2-3 VS dimensions, and larger tumors.

In routine practice, radiologists show poor agreement with volumetric results and sensitivity to detect interval change and overall poor accuracy for volumetric changes of ≤ ± 25% in volume. In the absence of volumetric measurements, radiologists need to be more diligent when evaluating interval changes in VS.