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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Roel Verhoeven (Pulmonary Diseases & Radiology, Radboudumc (Nijmegen), The Netherlands)
Chris de Korte (Medical Ultrasound Imaging Center (Radiology), Radboudumc (Nijmegen), The Netherlands)
Erik van der Heijden (Pulmonary Diseases, Radboudumc (Nijmegen), The Netherlands)

Abstract:
Background – For lung cancer staging, mediastinal lymph nodal spread needs to be assessed in a systematic and complete way. This is routinely done by EndoBronchial UltraSound – TransBronchial Needle Aspiration (EBUS-TBNA), a technique in which a flexible bronchoscope with an ultrasound transducer at the distal tip is inserted into the airways for ultrasound guided needle aspiration of the lymph node. Choosing which mediastinal lymph nodes are suspected and need to be aspirated for staging is currently based on FDG-PET avidity, and, CT- and ultrasound based nodal size. EBUS strain elastography (EBUS-SE) is a relatively new technique that may further help predict malignancy in these mediastinal lymph nodes. However, a standardized assessment strategy for EBUS-SE measurements is lacking. Objective - To determine an optimal assessment strategy of EBUS-SE measurements and to investigate its ability to predict mediastinal lymph node malignancy. Methods - Two qualitative visual analogue scale strain scores and two semi-quantitative strain elastography scores (mean strain histogram and strain ratio) were acquired in 120 lymph nodes suspected of lung cancer. After data collection, scorings were randomized into an 80% training dataset to determine scoring cut-off values. Performance was consecutively tested on the remaining 20% and the overall dataset. Results - Lymph nodes low in strain showed more likely to be malignant. The semi-quantitative strain histogram scoring strategy was able to best and most reproducibly predict malignancy with 93% overall sensitivity, 75% specificity, 69% positive predictive value, 95% negative predictive value, and, 82% accuracy. Combining the EBUS-SE histogram scoring with PET-CT information increased post-test likelihood of disease in relevant clinical scenarios, having a positive test likelihood ratio of 4.16 (2.98-8.13 95% CI) and a negative test likelihood ratio of 0.14 (0.04-2.81 95% CI) in suspicious lymph nodes based on PET- or CT imaging. Conclusions - EBUS Strain elastography can potentially help predict lymph node malignancy in patients with (suspected) lung cancer. In this pilot study, the best semi-quantitative assessment method showed to be the mean strain histogram technique. Standardization of strain elastography measurement acquisition is required to facilitate widespread clinical use of this technique.