Imaging criteria to predict Shamblin group in carotid body tumors - revisited.

This study aims to compare the imaging findings of carotid body tumors on contrast-enhanced computed tomography (CT) with the intraoperative Shamblin grade and to evolve an imaging-based scoring system that can accurately predict the Shamblin grade. Preoperative contrast-enhanced CT scans of 40 patients who underwent surgical excision of carotid body tumors in our institution between 2004 and 2017 were retrospectively reviewed. The angle of contact with the internal carotid artery (ICA), tumor volume, presence of peritumoral tuft of veins, loss of tumor adventitia interface and distance from the skull base were assessed and compared with the intraoperative Shamblin grades of the tumor. Ordinal logistic regression was used to determine which parameters could be predictors of the Shamblin grades. Receiver operator characteristic (ROC) curves were used to score the tumor volumes. Among the 42 tumors evaluated, 6 (14.3%) were surgically classified as Shamblin I, 15 (35.7%) as Shamblin II, and 21 (50%) as Shamblin III tumors. Pairwise comparison between the three Shamblin groups showed a statistically significant difference for angle of contact with ICA, maximum tumor dimension, presence of peritumoral tuft of veins and loss of tumor adventitia interface (p = 0.001, p = 0.001, p = 0.038 and p = 0.003, respectively). However, tumor volumes and distance from skull base were not significantly different between the Shamblin groups (p = 0.136 and p = 0.682). A scoring system, including four of the above mentioned parameters (angle of contact with ICA, tumor volume, presence of peritumoral tuft of veins, and loss of tumor adventitia interface) was developed with a maximum score of 8 and a minimum of 2. A statistically significant difference was found between the final scores among the three Shamblin groups (p < 0.001). Using ROC curves, a final score of ≥6 was found to separate Shamblin grade III tumors from grade I and II tumors (sensitivity, 95.24%; specificity, 71.43%). All patients with documented intraoperative estimated blood loss of >1000 mL had Shamblin grade III tumors. Postoperative complications like stroke, ICA thrombosis and lower cranial nerve palsies were seen only with Shamblin grade II and III tumors. The simple scoring system we have proposed correlates well with the Shamblin grade and helps in identifying patients who have a higher risk of developing complications.