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Lung Cancer Loris Ceron,1


The Challenge of Mediastinal Staging Lucio Michieletto,2


Andrea Zamperlin2


and Laura Mancino3


1. Director, Pulmonology Unit, Ospedale dell’Angelo Venice-Mestre; 2. Senior Registrar, Pulmonology Unit, Ospedale dell’Angelo Venice-Mestre; 3. Senior Registrar, Pulmonology Unit, Ospedale S Bortolo Vicenza


Abstract


Lung cancer staging is a crucial step in both correct prognosis and therapy. Mediastinal staging in particular is usually accomplished using imaging techniques such as computed tomography and 18F–glucose positron-emission tomography, minimally invasive techniques, i.e. transbronchial needle aspiration with or without ultrasound guidance (endobronchial ultrasound) and transoesophageal ultrasound-guided fine needle aspiration and surgical procedures, i.e. mediastinoscopy, thoracoscopy. Each of these techniques has its own sensitivities, specificities and predictive values that must be thoroughly considered within the staging route, with the aim of achieving the best result with the least resource consumption and the least discomfort to the patient; the correct evaluation of a negative result on the basis of its predictive value is essential as well. In this article we suggest a mathematical model that can predict the probability of nodal metastasis after a certain number of diagnostic procedures has been performed, providing an objective way of evaluating whether a patient is fit for surgery or, conversely, whether further investigations are required.


Keywords


Transbronchial needle aspiration, transoesophageal fine-needle aspiration, mediastinoscopy, positron-emission tomography, computed tomography, Bayes’ theorem


Disclosure: The authors have no conflicts of interest to declare. Received: 31 July 2010 Accepted: 27 January 2011 Citation: European Oncology & Haematology, 2011;7(1):31–5 Correspondence: Loris Ceron, Pulmonology Unit, Ospedale dell’Angelo, Via Paccagnella 11, 30174 Mestre-Venice, Italy. E: loris.ceron@ulss12.ve.it


Mediastinal staging in non-small-cell lung cancer (NSCLC) is crucial for correct prognosis and therapeutic choices. When no distal metastases are present, mediastinal involvement is the most important prognostic factor;1


therefore, mediastinal exploration represents an important resource-consuming step in patient evaluation. Ruling out mediastinal nodal involvement allows the patient to be considered for surgery; otherwise, complementary options such as chemotherapy or radiotherapy must be evaluated, subsequent surgery being suggested only when downstaging is achieved. The term clinical staging or pre-operative staging is commonly used in comparison with pathological staging, achieved during surgical intervention, which represents the gold standard in lung cancer staging.


Nowadays, several techniques are available for pre-operative mediastinal staging. The techniques can be separated into: imaging techniques, such as contrast-enhanced computed tomography (CT) and positron-emission tomography (PET); minimally invasive techniques, such as transbronchial needle aspiration (TBNA), endobronchial ultrasound (EBUS)-guided TBNA and endoscopic ultrasound (EUS)- guided fine-needle aspiration (FNA); and surgical techniques, such as mediastinoscopy, mediastinotomy and thoracoscopy.


Some of these techniques – PET, mediastinoscopy and EUS-FNA – provide very sensitive and specific results. TBNA alone, on the other hand, although highly specific, has not proved to be sufficiently sensitive and may provide false-negative results; its performance improves when supported by EBUS.


© TOUCH BRIEFINGS 2011


Available Techniques Computed Tomography


Alongside standard chest X-ray, CT is currently considered the fundamental preliminary examination when evaluating lung cancer. Contrast-enhanced chest CT is highly accurate in detecting lymph node enlargement, although a high interobserver variability rate may exist.2


The literature reports good specificity of CT (about 80%) and moderate sensitivity (not above 60%).3


This may imply that an enlarged


mediastinal lymph node (short axis ≥1cm) in a patient affected by lung cancer may in fact be healthy in four cases out of 10, whereas metastasis may be found in up to 20% of patients with normal size lymph nodes (short axis <1cm). Therefore, secondary neoplastic localisation cannot be diagnosed uniquely on the basis of the dimensions of the lymph nodes,4


and CT thus plays a central role in


guiding the choice of the most appropriate procedure for node biopsy. Accordingly, the recent American College of Chest Physicians (ACCP) guidelines on mediastinal staging report that CT may be considered sufficient only in cases of massive mediastinal invasion; in any other cases, further diagnostic techniques should be implemented.5


Positron-emission Tomography


PET is probably the most revolutionary diagnostic technique of the last 20 years in the investigation of NSCLC.6–9


Its sensitivity and specificity


are 75–91% and 78–93%, respectively, depending on lymph node size.10 Its overall sensitivity and negative predictive value are comparable to those of mediastinoscopy, such that mediastinal negativity on PET paves the way to the use of surgery with no need for further


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