Invasive mediastinal staging by endosonography or video-assisted mediastinoscopy in PET-CT clinical N1 non-small cell lung cancer

Patients with clinical N1 (cN1) non-small cell lung cancer (NSCLC) based on PET-CT imaging are often found to have occult mediastinal nodal involvement (N2-disease) at invasive staging or resection although the PET-CT was negative on the mediastinum. Two multicenter prospective studies in patients with PET-negative mediastinum but suspected cN1-disease were performed to measure sensitivity of two invasive mediastinal staging strategies to detect mediastinal nodal disease, one with endosonography and one with video-assisted mediastinoscopy (VAM) or video-assisted mediastinoscopic lymphadenectomy (VAMLA). Consecutive patients with operable and resectable cN1 (suspected) NSCLC underwent endosonography, if negative followed by mediastinoscopy in the first study (n=100). In the second study with identical inclusion criteria, patients (n=105) underwent a VAM or VAMLA [VAM(LA)]. All patients underwent FDG-PET and CT scan prior to invasive mediastinal staging. The primary study outcome was sensitivity to detect N2-disease. Secondary endpoints were the prevalence of N2-disease, negative predictive value (NPV) and accuracy of the invasive staging procedure. In both studies, 25% of patients with cN1 disease on imaging had eventually pathology-proven N2-disease. Endosonography alone reached a sensitivity (38%) to detect mediastinal nodal disease. Invasive mediastinal staging with VAM(LA) had a sensitivity of 73% to detect N2-disease. The NPV was 92% and accuracy 93%. At endosonography, a mean of 2.1 mediastinal nodal stations were biopsied vs. 3.9 at VAM(LA). VAM(LA) has a satisfactory sensitivity of 73% to detect mediastinal nodal disease in cN1 lung cancer and could be the technique of choice for pre-resection mediastinal lymph node assessment in this patient group with a one in four chance of occult positive mediastinal nodes after negative PET-CT.