Comparison of Endobronchial Ultrasound, Positron Emission Tomography, and CT for Lymph Node Staging of Lung Cancer
Lung cancer is the most common cause of cancer related death in the Western world. The outcomes of the disease vary depending on early detection, histologic types of malignancy, and staging. Screening tests for early detection of lung cancer including low-dose spiral CT, sputum cytology screening, and autofluorescent bronchoscopy may increase the number of patients eligible for surgical resection. Histologic type of lung cancer can be diagnosed in 70 to 85% of patients by bronchoscopic and other noninvasive procedures. However, staging depends mainly on imaging procedures. Malignant involvement of the mediastinum is a highly significant prognosis factor for survival. Therefore, better preoperative staging will limit unnecessary surgical interventions, and patients will benefit more from surgical resection. Current American Thoracic Society guidelines for the staging of lung cancer suggest that contrast-enhanced CT should be considered the standard imaging technique for the evaluation of the mediastinum. Lymph nodes with the short-axis diameter > 1 cm on CT are suspected to be malignant, However, CT is neither sensitive nor specific for detecting metastasis in the mediastinum, since some benign nodes may be larger and small lymph nodes may be malignant. Hence, additional imaging such as positron emission tomography (PET) with F-fluorodeoxyglucose (FDG) is required for a precise evaluation of the mediastinum. A metaanalysis comparing the test performance of FDG-PET and CT for mediastinal staging in patients with non-small cell lung cancer showed that FDG-PET is more accurate than CT for mediastinal staging. However due to the limited diagnostic specificity for identifying mediastinal metastases, tissue proof of PET-positive lesions are recommended to prove that the lesions are truly malignant before denying surgical resection. Tissue proof can be obtained by mediastinoscopy, the “gold standard” for mediastinal staging in lung cancer. However, it is invasive, requires general anesthesia, and often hospitalization. Therefore, different minimally invasive methods have been applied for tissue sampling. Conventional broncho-scopic transbronchial needle aspiration (TBNA) is a well-established technique, but the yield varies wide-ly. Efforts have been made to improve the yield by adding CT fluoroscopy guidance or the radial-type endobronchial ultrasound (EBUS) probe guidance. Furthermore, endoscopic ultrasound (EUS) with fine-needle aspiration (EUS-FNA) has been reported to have a high yield in the diagnosis of mediastinal lymph nodes. However, all of these methods have limitations. Another new minimally invasive method of mediastinal biopsy is direct real-time EBUS-guided TBNA using the convex probe (CP)-EBUS- The aim of the present study was to compare the accuracy of the different staging tests (CT, PET, and EBUS-TBNA) for correct staging of the mediastinum in patients with lung cancer considered to be operable.