Calculating the Tumor Volumes in Vestibular Schwannomas: Are the ABC/2 and Volumetric Methods Comparable?

Purpose: To assess the efficacy of the ABC/2 method for calculating the volume of vestibular schwannomas as compared with 3-D planimetric method.

Study Design: Retrospective.

Methods: Fifty eight cases of pathologically confirmed sporadic vestibular schwannomas (VS) were analyzed. Tumors volumes were calculated for each tumor twice, once through semiautomated 3-D volumetric method and subsequently through ABC/2 (AP × ML × CC/2) methodology after calculating the maximal tumor dimensions in anteroposterior (AP), coronal (ML), and craniocaudal (CC) dimensions. Tumor volumes were initially correlated as a group and subsequently by dividing them into three groups using the Hannover classification.

Results: The two methodologies were highly correlated when tumors were analyzed as a group (rho = 0.913, p < 0.0001). In the sub-group analysis, tumor volumes were again strongly correlated for larger tumors (rho = 0.918, p < 0.0001) but the correlation progressively reduced as tumor volumes decreased.

Conclusion: Given the ease and universal accessibility of linear measurement applications, the ABC/2 methodology is a robust substitute for calculating tumor volumes, especially for larger tumors.