Clinical Applications of Endobronchial Ultrasound (EBUS) Scope: Challenges and Opportunities

Added value of EUS-B-FNA to bronchoscopy and EBUS-TBNA in diagnosing and staging of lung cancer

Background

Bronchoscopy and EBUS are standard procedures in lung cancer work-up but have low diagnostic yield in lesions outside the central airways and hilar/mediastinal lymph nodes. Growing evidence on introducing the EBUS endoscope into the oesophagus (EUS-B) in the same session as bronchoscopy/EBUS gives access to new anatomical areas that can be safely biopsied.

Objective

To summarize the current evidence of the added value of EUS-B-FNA to bronchoscopy and EBUS-TBNA in lung cancer work-up.

Methods

A narrative review.

Results

Few randomized trials or prospective studies are available. Prospective studies show that add-on EUS-B-FNA increases diagnostic yield when sampling abnormal mediastinal lymph nodes, para-oesophageal lung and left adrenal gland. A large retrospective series on EUS-B-FNA from retroperitoneal lymph nodes suggests high diagnostic yield without safety concerns, as do casuistic reports on EUS-B-FNA from mediastinal pleural thickening, pancreatic lesions, ascites fluid and pericardial effusions. No study has systematically assessed both diagnostic yield, safety, patient reported outcomes, adverse events and costs.

Conclusion

The diagnostic value of add-on EUS-B to standard bronchoscopy and EBUS in lung cancer work-up appears very promising without safety concerns, giving the pulmonologist access to a variety of sites out of reach with other minimally invasive techniques. Little is known on patient-reported outcomes and costs. Future and prospective research should focus on effectiveness aspects to clarify whether overall benefits of add-on EUS-B sufficiently exceed overall downsides.

Utility of SHOX2 and RASSF1A gene methylation detection on the residual cytology material from endobronchial ultrasound-guided transbronchial needle aspiration

Objective

This study aims to assess the effectiveness of Short Stature Homeobox 2 (SHOX2) and RAS Association Domain Family 1 Isoform A (RASSF1A) gene methylation detection in residual liquid-based cytology (LBC) materials from Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration (EBUS-TBNA) and investigate the diagnostic accuracy of a comprehensive diagnostic approach.

Material and Methods

Between June 2022 and May 2023, a total of 110 cases that underwent EBUS-TBNA were enrolled in the study. SHOX2 and RASSF1A genes methylation detection using the residual cytological material, LBC, and cell block (CB) were conducted for each EBUS-TBNA case. The sensitivity and specificity of cytology, CB histopathology, SHOX2, and RASSF1A methylation in diagnosing EBUS-TBNA samples were determined based on follow-up data.

Results

Among the 72 cases confirmed as pulmonary carcinomas, the methylation test yielded positive results in 24 adenocarcinoma cases, 10 squamous cell carcinoma cases, and 14 small cell carcinoma cases. The sensitivity of the comprehensive diagnosis (combining LBC, CB, and methylation detection) in distinguishing metastatic pulmonary epithelial malignancies in mediastinal and hilar lymph nodes or masses from benign lesions was higher (97.22%, 70/72) than that of morphological diagnosis alone (LBC and CB) (88.89%, 64/72; P < 0.05).

Conclusion

SHOX2 and RASSF1A methylation detection demonstrates a high sensitivity and negative predictive value in the identification of pulmonary epithelial malignancies and holds promise as a valuable ancillary approach to enhance morphological diagnosis of EBUS-TBNA.

EBUS-guided cryobiopsy in the diagnosis of thoracic disorders

BACKGROUND

Endobronchial Ultrasound (EBUS) has emerged as a crucial tool for diagnosing intrathoracic disorders, particularly in the staging of lung cancer. However, its diagnostic capabilities in the context of benign and rare diseases remain a subject of debate.

AIM

to investigate the diagnostic yield and safety of EBUS-transbronchial mediastinal cryobiopsy (EBUS-TMC) in comparison to EBUS-transbronchial needle aspiration (TBNA) for a broad spectrum of intrathoracic diseases.

METHODS

a single-centre retrospective observational study conducted on 48 patients who underwent both EBUS-TBNA and endobronchial ultrasound-transbronchial mediastinal cryobiopsy (EBUS-TMC) in the same procedure between August 2021 and October 2023.

RESULTS

The overall diagnostic yield of EBUS-TMC surpassed that of EBUS-TBNA (95.8% vs 54.1 %), notably excelling in the diagnosis of sarcoidosis (92.8% vs 78.5 %), rare mediastinal disorders (100% vs 0 %), hyperplastic lymphadenopathy (100% vs 0 %), and lymphoproliferative disease (100% vs 0 %). No significant differences were observed in the diagnosis of NSCLC and SCLC. Samples obtained through EBUS-TMC facilitated the acquisition of NGS and immunohistochemical analyses more readily.

CONCLUSION

EBUS-TMC may contribute to the precise diagnosis and subtyping of mediastinal diseases, especially lymphomas and rare mediastinal tumors, thereby reducing the number of non-diagnostic procedures.

The evolution of endobronchial ultrasound usage in modern era

Over the past two decades, endobronchial ultrasound (EBUS) has become a crucial tool for diagnosing pulmonary diseases. The most common indication of EBUS usage is the diagnosis and staging of lung cancer. Additionally, there have been significant improvements in the application of convex probe EBUS in line with the increase in experience and knowledge about EBUS and the developments in medicine and technology. To enhance diagnostic accuracy and acquire larger tissue samples, techniques such as cryo-biopsy guided by endobronchial ultrasound (EBUS) and intranodal forceps biopsy have been developed. Additionally, elastography functionality has been integrated into the EBUS application to improve the assessment of targeted lesions. Moreover, its utilization for evaluating and sampling pulmonary vascular structures has expanded. It has also found applications in guiding intratumoral therapy, positioning fiducial markers, and facilitating the drainage of pleural or pericardial effusions. This review aims to provide an overview of the extended applications of convex probe EBUS beyond its conventional uses.