Added Value of Computed Tomography to Ultrasonography for Assessing LN Metastasis in Preoperative Patients with Thyroid Cancer: Node-By-Node Correlation.

Roh-Eul Yoo,Ji-Hoon Kim,Koung Mi Kang,Sun-Won Park,Seung Hong Choi,Tae Jin Yun,Chul-Ho Sohn,Inpyeong Hwang

doi:10.3390/cancers12051190

Abstract

Diagnostic accuracy of US in the evaluation of lymph node (LN) metastasis for thyroid cancer patients is limited. We investigated the value of CT added to US for characterizing LNs in preoperative thyroid cancer patients by node-by-node correlation. A total of 225 primary thyroid cancer patients who underwent LN biopsy were included. Based on node-by-node correlation, 274 LNs were classified into probably benign, indeterminate, and suspicious categories on US, CT, and combined US/CT. Malignancy risks were calculated for each category and were compared between US/CT concordant and discordant cases. On US, CT, and combined US/CT, malignancy risks were 1.7%, 8.7%, and 0% in the probably benign category, 22.4%, 5.9%, and 8.0% in the indeterminate category, and 77.2%, 82.0%, and 75.6% in the suspicious category, respectively. Malignancy risk of the concordant suspicious category was higher than that of the discordant suspicious category (84.7% vs. 43.2%, p < 0.001). The addition of CT helped correctly detect additional metastasis in 16.4% of the US indeterminate LNs and in 1.7% of the US probably benign LNs. CT may complement US for LN characterization in thyroid cancer patients by suggesting the diagnostic confidence level for the suspicious category and helping correctly detect metastasis in US indeterminate LNs.

Highlights

Owing to its wide availability and high-resolution as well as the lack of exposure to ionizing radiation, ultrasonography (US) has been established as the mainstay in the diagnostic imaging work-up during the preoperative evaluation of lymph node (LN) metastasis according to various international guidelines [1,7,8,9,10,11,12]
Many studies have reported that the US does not have sufficient accuracy for the diagnosis of LN metastasis [13,14,15,16]
All of the previous studies were performed on the basis of level-by-level analysis, and the reason why the combination of US and CT had a higher sensitivity and accuracy was not clear, other than the ability of CT to detect additional LN metastasis in US blind spots

Summary

Introduction

Despite the low mortality rate of papillary carcinoma (PTC) patients, the rates of cervical lymph node (LN) metastases at initial presentation and the time of recurrence have been reported to be relatively high, and accurate preoperative imaging diagnosis of LN metastasis has been considered key to reducing the chance of repetitive surgery and operation-related morbidity [1,2,3,4,5,6].Owing to its wide availability and high-resolution as well as the lack of exposure to ionizing radiation, ultrasonography (US) has been established as the mainstay in the diagnostic imaging work-up during the preoperative evaluation of LN metastasis according to various international guidelines [1,7,8,9,10,11,12]. Many studies have reported that the US does not have sufficient accuracy for the diagnosis of LN metastasis [13,14,15,16]. Several articles have reported that the combination of US and CT (computed tomography) has a significantly higher sensitivity than the US alone without a significant difference in specificity, supporting the complementary role of CT in the preoperative LN evaluation [21,22,23,24]. All of the previous studies were performed on the basis of level-by-level analysis, and the reason why the combination of US and CT had a higher sensitivity and accuracy was not clear, other than the ability of CT to detect additional LN metastasis in US blind spots (e.g., the mediastinum or retropharyngeal area)

Objectives

Methods

Results

Discussion

Conclusion