Diagnostic Performance of Endosonography to Detect Mediastinal Lymph Node Metastasis in Patients with Radiological N1 Non–Small Cell Lung Cancer

PURPOSE: Guidelines recommend that non–small cell lung cancer (NSCLC) patients with suspected hilar lymph node (LN) metastases should undergo invasive mediastinal LN staging prior to surgical treatment via endosonography. We evaluated the diagnostic performance of endosonography for detecting occult mediastinal metastases (OMM) and determined the factors associated with OMM in NSCLC patients with radiological N1. MATERIALS AND METHODS: Patients with confirmed primary NSCLC with radiological N1 who underwent endosonography for nodal staging assessment from January 2013 to December 2019 were retrospectively analyzed. RESULTS: The prevalence of OMM was found to be 83/279 (29.7%) and only 38.6% (32/83) were diagnosed via endosonography. However, five of them were confirmed as N3 by endosonography. The overall diagnostic sensitivity, negative predictive value, accuracy, and area under the curve of endosonography were 38.6%, 79.4%, 81.7%, and 0.69, respectively. In multivariable analysis, central tumor (adjusted odds ratio [aOR], 2.05; 95% confidence interval [CI], 1.15 to 3.68; p=0.016), solid tumor (aOR, 10.24; 95% CI, 1.32 to 79.49; p=0.026), and adenocarcinoma (aOR, 3.01; 95% CI, 1.63 to 5.55; p < 0.001) were related to OMM in radiological N1 NSCLC patients. CONCLUSION: Although the sensitivity of endosonography for detecting OMM was only 40%, the prevalence of OMM was not low (30%) and some cases even turned out to be N3 diseases. Clinicians should be aware that OMM may be more likely in patients with central, solid, and adenocarcinomatous tumor when performing nodal staging in radiological N1 NSCLC via endosonography.