Optimal Endobronchial Ultrasound Strain Elastography Assessment Strategy: An Explorative Study

Abstract

Background: In lung cancer staging, mediastinal lymph nodes are currently aspirated using endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA) based on size and FDG-PET avidity. EBUS strain elastography (SE) is a new technique that may help predict the presence of malignancy. However, a standardized assessment strategy for EBUS-SE measurement is lacking. Objectives: The aim of this study was to determine the optimal assessment strategy for investigating the predictive value of EBUS-SE in mediastinal lymph nodes. Methods: Two qualitative visual analogue scale strain scores and two semiquantitative strain elastography measurements (a strain histogram and strain ratio) were acquired in 120 lymph nodes of 63 patients with (suspected) lung cancer. The dataset was randomized into an 80% training dataset to determine cut-off values. Performance was consecutively tested on the remaining 20% and the overall dataset. Results: The semiquantitative mean histogram scoring strategy with a cut-off value of 78 (range 0–255) showed the best and most reproducible performance in prediction of malignancy with 93% overall sensitivity, 75% specificity, 69% positive predictive value, 95% negative predictive value, and 82% accuracy. Combining the EBUS-SE mean histogram scoring outcome with PET-CT information increased the post-test probability of disease in relevant clinical scenarios, having a positive test likelihood ratio of 4.16 (95% CI 2.98–8.13) and a negative test likelihood ratio of 0.14 (95% CI 0.04–2.81) in suspicious lymph nodes based on FDG-PET or CT imaging. Conclusions: EBUS-SE can potentially help predict lymph node malignancy in patients with lung cancer. The best semiquantitative assessment method is the mean strain histogram technique.

Predictive Value of Endobronchial Ultrasound Strain Elastography in Mediastinal Lymph Node Staging: The E-Predict Multicenter Study Results

“…SE is a relative measure and can therefore vary with measurement technique and time. Standardization and training are important for EBUS-SE implementation [12]. In this study, the performance variability of EBUS-SE was found to be insignificant between centers and operators.…”

“…EBUS-SE measurements of to-be-aspirated lymph nodes were acquired at the discretion of the endoscopist. A standardized measurement protocol using the strain histogram scoring technique DOI: 10.1159/000507592 was used to quantify measured lymph node strain as previously reported in more detail [see 12,13]. Compared to previously published data [12], the EBUS-SE software settings were updated.…”

“…A standardized measurement protocol using the strain histogram scoring technique DOI: 10.1159/000507592 was used to quantify measured lymph node strain as previously reported in more detail [see 12,13]. Compared to previously published data [12], the EBUS-SE software settings were updated. As such, the EBUS-SE mean strain cutoff was re-analyzed for optimal performance in the present study.…”

“…No central reading on FDG-PET was performed. Strain measurement reproducibility was furthermore scored subjectively by the operator as "heavily changing," "slightly changing," or "reproducible" based on the strain rate graph and corresponding color overlays [12].…”

“…Several qualitative and semi-quantitative techniques to assess the calculated relative strain have been reported. We recently showed that the strain histogram method will give the best overall accuracy for predicting lymph node malignancy, as it is the most operator-independent and thus objective technique [12]. More detailed information on EBUS-SE assessment technique and SE technology can also be found in the previous publication and its online supplementary material [12,13].…”