Comparison of ultrasonography and CT for preoperative nodal assessment of patients with papillary thyroid cancer: diagnostic performance according to primary tumor size

Abstract

Background Indications for computed tomography (CT) in preoperative patients with thyroid cancer are still controversial. Purpose To determine the value of CT and ultrasonography (US) in preoperative lymph node assessment of patients with papillary thyroid carcinoma (PTC) according to primary tumor size. Material and Methods A total 453 patients with surgically proven PTC who underwent US and CT for preoperative evaluation in 2010 at our tertiary referral center were included. The diagnostic sensitivity, specificity, and accuracy of US, CT, and the combination of US and CT (US/CT) in the preoperative nodal assessment were compared. We performed subgroup analysis to compare the findings according to primary tumor size. Results In overall tumors, adding CT to US had greater sensitivity, lower specificity, and greater accuracy in predicting central lymph node metastasis (LNM) but lower accuracy in prediction of lateral LNM. In smaller cancers (≤1 cm), US alone had greater specificity and accuracy than CT alone or US/CT in predicting lateral LNM. In larger cancers (>1 cm), CT had greater sensitivity and accuracy than US in predicting central LNM, while US had greater specificity and accuracy than CT in predicting lateral LNM. There were no patients with smaller tumors who showed retropharyngeal and superior mediastinal LNM diagnosed by CT alone. Conclusion CT is superior to US for detecting central LNM in preoperative patients with PTCs > 1 cm. However, there are no benefits to adding CT to US to predict lateral LNM in small cancers (≤1 cm).