SC19.02 Invasive Staging of Lung Cancer: EBUS, EUS and Beyond

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Despite the advances in surgical treatment and multimodality treatment, lung cancer is still the leading cause of death from malignant disease worldwide. Accurate staging is important not only to determine the prognosis but also to decide the most suitable treatment plan. During the staging process of non-small cell lung cancer (NSCLC), mediastinal lymph node staging is one of the most important factors that affect the patient outcome. Non-invasive staging such as computed tomography (CT) and positron emission tomography (PET) indicate size and metabolic activity, respectively. However imaging alone is inaccurate and therefore tissue sampling is the preferred and most reliable. Surgical staging by mediastinoscopy has been the gold standard for mediastinal lymph node staging but requires general anesthesia and complications cannot be ignored. Endoscopic ultrasound techniques provide a minimally invasive alternative for surgical staging. The current available endoscopic ultrasound techniques for mediastinal staging include transesophageal endoscopic ultrasound guided fine needle aspiration (EUS-FNA) and endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA). Both procedures can be performed in an outpatient setting under local anesthesia. EUS-FNA is a sensitive and safe method of evaluating the inferior mediastinal nodes (stations 7, 8, and 9) and some parts of the anterior mediastinal nodes if the lymph nodes are accessible from the esophagus. However, in spite of the strength of EUS-FNA for evaluating the inferior mediastinal nodes, its ability to evaluate lesions anterior to the trachea is limited. On the other hand, EBUS-TBNA has reach to the paratracheal and subcarinal (stations 2R, 2L, 4R, 4L, 7), as well as the N1 lymph nodes (stations 10, 11, 12). In experienced hands, EBUS can be used through the esophagus for a EUS-like approach to the inferior mediastinal lymph nodes. Thus, EUS-FNA and EBUS-TBNA are complementary methods for lymph node staging in lung cancer and most of the mediastinum and the hilum can be evaluated with these endoscopic procedures. Aortic nodes (stations 5 and 6) are exceptions and must be evaluated by surgical methods (anterior mediastinotomy, VATS, thoracotomy). Based on the current evidence, EBUS-TBNA and EUS-FNA presents a minimally invasive endoscopic procedure as an alternative to mediastinoscopy for mediastinal staging of NSCLC with discrete N2 or N3 lymph node enlargement, provided negative results are confirmed by surgical staging. EBUS-TBNA can access all lymph nodes accessible by mediastinoscopy as well as hilar (N1) lymph nodes. EUS-FNA has access to the inferior mediastinal lymph nodes not accessible by mediastinoscopy. EBUS-TBNA and/or EUS-FNA have in fact replaced mediastinoscopy in many patients with diffuse mediastinal adenopathy, where a simple tissue diagnosis is required to determine treatment. When combined the techniques offer safe and accurate assessment of mediastinum, with accuracy surpassing that of the pervious gold standard – cervical mediastinoscopy. EBUS-TBNA and/or EUS-FNA can also be repeated with ease and have been used for mediastinal restaging in patients who underwent neoadjuvant therapy in preparation for definitive surgical intervention. Ultrasound image analysis of lymph nodes may assist bronchoscopists during EBUS-TBNA or EUS-FNA. Standard sonographic classification of lymph nodes can help characterize mediastinal and hilar lymph nodes as benign or malignant, which may guide the decision on which lymph nodes to sample. Newer imaging technology such as elastography can potentially enhance US guided image analysis of the lymph nodes.