Analysis of vestibular schwannoma size: A literature review on consistency with measurement techniques

• Vestibular schwannoma tumor size is closely analyzed in patients undergoing observation or treatment.
• We examine the use of described measurement techniques in large published clinical series to assess their consistency.
• Linear measurements are more common, but the technique is variable and an inaccurate estimate of three-dimensional tumor size.
• Volumetric assessments have the greatest clinical utility, sensitivity and accuracy in measuring tumor size and growth.
• Standardization of volume assessments will provide the best method for producing consistent literature findings.

IntroductionVestibular schwannoma (VS) tumor size, a significant prognostic indicator, is closely analyzed in patients undergoing observation or treatment. It has historically been reported in terms of linear size; however, volumetric assessments can now be performed routinely. We examine the use of described measurement techniques in large published clinical series to assess their consistency.MethodsComputerized searches of the MEDLINE database (Pubmed) from 1975 to August 2014 were conducted with the purpose of identifying large series describing the management of VSs. Articles that reported tumor size measurements were included if they described greater than 600 patients.Results19 studies were found fitting the inclusion criteria, consisting of large retrospective studies with sample sizes ranging from 614 to 2991. A total of 17 studies reported linear measurements, while 2 studies reported volumetric assessments of tumor size. Significant variations were found regarding methods for linear measurement. Furthermore, several papers did not provide any details regarding the measurement technique. Inclusion of intracanalicular portions of the tumor was highly variable. Volume assessments were performed by segmented volume analysis.ConclusionsAmong the large published series on VSs, significant variation exists regarding the utilized measurement technique to assess size. Volumetric assessments have the greatest clinical utility, sensitivity and accuracy in measuring tumor size and growth. Standardization of volume assessments will provide the best method for producing consistent literature findings.