Background : The observation made by the ASTER investigators might be criticized as all procedures were performed in highly experienced centers. To date, the number of mediastinoscopies needed to detect one additional N2/3 disease in the routine clinical practice of chest physician performing endosonography for mediastinal staging is unknown. The investigators therefore seek to answer whether a negative endosonography should routinely be followed by mediastinoscopy in day to day clinical practice.~Aim : As the use of endoscopic ultrasonography for mediastinal diagnosis and/or staging is widely spread in Belgium, the investigators aimed to determine the number of mediastinoscopies needed to detect one additional mediastinal lymph node invasion during routine clinical practice.~Setting : centers in Belgium with EBUS-TBNA and/or EUS-FNA experience in at least 20 patients agreed to participate and will include their patients.~Design : Prospective national observational multicenter study. All patients with clinical N2/3 disease based on CT and/or PET requiring invasive mediastinal staging will primarily undergo invasive mediastinal staging with endosonography (EBUS +/- EUS). A subsequent cervical mediastinoscopy will be performed in case no mediastinal lymph node involvement was found with endosonography. Local surgeons perform these procedures according to their institutional practice. Thoracotomy with mediastinal lymph node dissection will be the gold standard for invasive mediastinal staging, in case no mediastinal lymph node metastases were found during clinical staging including endosonography and mediastinoscopy.~Patients : The study will include 255 patients, based on the calculation of 15 consecutive patients in each participating center, in order to validate the ASTER data.~Primary endpoint : The number of mediastinoscopies needed to detect one additional N2/3.~Secondary endpoints : The number of mediastinal lymph nodes stations sampled with endosonography ; the median size of largest mediastinal lymph node sampled; characteristics of mediastinal nodal disease missed by endosonography.
As the use of endoscopic ultrasonography for mediastinal diagnosis and/or staging is widely spread in Belgium, the investigators aimed to determine the number of mediastinoscopies needed to detect one additional mediastinal lymph node invasion during routine clinical practice in the staging of potentially resectable clinical stage III non-small cell lung cancer.