S968 Quantitative Analysis/Tissue Characterization for Malignant Lymph Nodes Using Endoscopic Ultrasound Elastography (EUS-EG)

Abstract

Introduction: Endoscopic Ultrasound Elastography (EUS-EG), has emerged as a useful modality in estimating tissue stiffness. Second generation techniques for elastography assessment allow quantitative measurements of average elasticity of a lesion. The strain ratio (SR) elastography is a semi-quantitative measure of elastography patterns. This ratio is calculated by comparing the elastography patterns of the targeted lymph nodes (LN) to those of a nearby reference tissue. With help of this study we can improve diagnostic accuracy of EUS-EG in evaluation of malignant LN. The objective of this study is to assess the specificity, sensitivity and predictive values of the stain ratio (SR) measured by EUS-EG in differentiating benign from malignant lymph nodes (LNs). Methods: This prospective study included 106 patients with Abdominal/Mediastinal lymphadenopathy. Second generation EUS-EG was performed, in addition to detailed assessment of sonographic features of LN including: size, diameter, character, shape, echotexture (echogenic or echo-poor) and hilum (lost or preserved). Strain ratio was calculated by EUS-EG ((Pentax EG-3830UT Echo-endoscope, HOYA Corporation, PENTAX Lifecare Division, Hitachi EUB-7000 ). Strain Ratio cut off was calculated on basis of receiver operating characteristic (ROC) curve analysis. Results: Majority of study population were males: 64 (60.4%).Mean age of 46.3 ± 15.5 years. Mean size of lymph nodes was 22.2 ± 7.7 mm and mean strain ratio was 61.9 ± 46.3. In total 36 (34 %) patients had malignant lymphadenopathy on histopathology in which 88.8% were found to be hard on elastography. At cut off 27, strain ratio demonstrated sensitivity, specificity, positive and negative predictive values of 80.5 %, 58.7 %, 85.2% and 66.04%, respectively with area under the ROC (AUROC) of 0.72.On multivariate analysis, higher strain ratio (p=0.002) and lymph node size ≥20 mm (p=< 0.001) were found to be significantly associated with presence of malignant disease. Conclusion: Although histology remains the gold standard for diagnosis, EUS-EG strain ratio is a useful technique to predict malignancy in restrained settings where biopsy is not possible which includes; vascular proximity and/ chances of seedling. Moreover, Strain ratio can also be utilized in disease staging. We demonstrated that lymph node size ≥ 20 mm and EUS-EG strain ratio ≥ 27.1, has higher likelihood of malignancy.Figure 1.: Receiver operating characteristic (ROC) curve for EUS-EG Strain Ratio cut off 27 (AUROC= 0.72)