908 Diagnostic Value of Semi-Quantitative Endoscopic Ultrasound Elastography in the Evaluation of Mediastinal and Abdominal Lymph Nodes

Abstract

INTRODUCTION: An accurate differentiation between benign and malignant lymph nodes (LN) is crucial for staging, risk stratification and treatment selection in patients with gastrointestinal malignancies. Endoscopic ultrasound (EUS) elastography can offer additional information that enables a better tissue characterization, enhancing the diagnostic power of EUS. The aim of this study was to evaluate the accuracy of the qualitative elasticity scores (ES) and semi-quantitative strain ratio (SR) for the diagnosis of abdominal and mediastinal LNs. METHODS: Consecutive patients referred for EUS evaluation of a mediastinal or abdominal LN by a single endosonographer (MSB) at a tertiary cancer center between January 2018 and May 2019 were included in the study. Elasticity scores (Table 1) and SR were determined during EUS exam. The final diagnosis was obtained by EUS-FNA cytology evaluation, surgical pathologic examination or clinical follow up. RESULTS: A total of 45 patients undergoing EUS evaluation of 70 LNs (40 benign, 30 malignant) were included in the analysis. According to the qualitative ES, the elastography images were interpreted as benign in 18 cases, malignant in 33 cases and indeterminate in 19. ES alone had a sensitivity of 100% and a specificity of 60% (Table 1). Based on the ROC curve analysis results, the best cut-off of SR to obtain the maximum area under the curve was 18.9, with a sensitivity of 47% and specificity of 85%. When both ES and SR were considered, the sensitivity was 100% with a specificity of 60% and negative predictive value of 100%. CONCLUSION: EUS elastography represents a promising method that allows the differential diagnosis of benign and malignant LN and it is complimentary to EUS-FNA. Given the high negative predictive value, EUS-elastography can decrease the number of unnecessary biopsies. The elasticity score and SR may be useful in patients with negative EUS-FNA results or in case in which a biopsy is not feasible.