Diameter-Based Volumetric Models May Inadequately Calculate Jugular Paraganglioma Volume Following Sub-Total Resection

Background: As gross total resection of jugular paragangliomas (JPs) may result in cranial nerve deficits, JPs are increasingly managed with subtotal resection (STR) with postoperative radiological monitoring. However, the validity of commonly used diameter-based models that calculate postoperative volume to determine residual tumor growth is dubious. The purpose of this study was to assess the accuracy of these models compared to manual volumetric slice-by-slice segmentation. Methods: A senior neuroradiologist measured volumes via slice-by-slice segmentation of JPs pre- and postoperatively from patients who underwent STR from 2007 to 2019. Volumes from three linear-based models were calculated. Models with absolute percent error (APE) > 20% were considered unsatisfactory based on a common volumetric definition for residual growth. Bland-Altman plots were used to evaluate reproducibility, and Wilcoxon matched-pairs signed rank test evaluated model bias. Results: Twenty-one patients were included. Median postoperative APE exceeded the established 20% threshold for each of the volumetric models as cuboidal, ellipsoidal, and spherical model APE were 63%, 28%, and 27%, respectively. The postoperative cuboidal model had significant systematic bias overestimating volume (p = 0.002) whereas the postoperative ellipsoidal and spherical models lacked systematic bias (p = 0.11 and p = 0.82). Conclusion: Cuboidal, ellipsoidal, and spherical models do not provide accurate assessments of postoperative JP tumor volume and may result in salvage therapies that are unnecessary or inappropriately withheld due to inaccurate assessment of residual tumor growth. While more time-consuming, slice-by-slice segmentation by an experienced neuroradiologist provides a substantially more accurate and precise measurement of tumor volume that may optimize clinical management.