Computed Tomography for Detecting Cervical Lymph Node Metastasis in Patients Who Have Papillary Thyroid Microcarcinoma with Tumor Characteristics Appropriate for Active Surveillance

Abstract

Background: Active surveillance (AS) has been considered one of the management options in patients with low-risk papillary thyroid microcarcinoma (PTMC). It is important to evaluate clinical lymph node (LN) metastasis to select appropriate candidates with low-risk disease. We investigated the predictive accuracy of computed tomography (CT) for cervical LN metastasis in patients who have PTMC with tumor characteristics appropriate for AS. Methods: This was a retrospective study. Medical records from December 2014 to the end of 2016 were reviewed. Patients who underwent thyroidectomy and who had pathologically confirmed PTMC were included. A total of 464 patients who had tumors with ultrasound (US) characteristics appropriate for AS and who underwent preoperative CT were included in the analysis. Results: CT showed higher diagnostic values especially in positive predictive value (PPV) than US. In patient-based analyses, CT showed low sensitivity and negative predictive value (NPV) (16.0% and 58.5%, respectively), but high specificity and PPV (99.6% and 97.1%, respectively) for detecting cervical LN metastasis. Similar trends were observed for the results of the central neck-level by CT (sensitivity, 14.9%; specificity, 97.4%; PPV, 82.9%; and NPV, 57.4%) in level-by-level analyses. When restricted to lateral neck levels, CT showed high diagnostic accuracy of 95.4% for detecting LN metastasis. In all analyses, CT showed better diagnostic values for cervical LN metastasis than US. Combining US and CT did not improve the diagnostic accuracy compared with CT. Conclusions: In patients with PTMC whose tumor has characteristics suitable for AS, CT had additional benefit after cervical LN assessment by US. Further studies are needed to evaluate routine initial CT scanning for patients who are candidates for AS.

Keywords: active surveillance; computed tomography; lymph node metastasis; papillary thyroid microcarcinoma; ultrasound.