N2 Disease in T1 Non-Small Cell Lung Cancer

Background: The optimal management strategy for mediastinal staging in early-stage non-small cell lung cancer (NSCLC) is not clearly defined. The true prevalence of mediastinal lymph node metastases (N2 disease) in resected pathologic T1 (pT1) NSCLC must be known to define the role of invasive mediastinal staging in these patients. Methods: Data of patients with pT1 lesions resected at Mayo Clinic between 1998 and 2006 were retrospectively reviewed. Patients with N2 disease were identified from pathology and operative reports. We reviewed demographics, radiologic data, and surgical procedures for those with pathologic T1 N2 NSCLC. Results: We identified 968 cases of pT1 lesions, 59 with pN2 disease (6.1%). For those with T1 N2 disease, the primary lung lesion was peripheral in 18 (31%) and central in 41 (69%). Of these, 36 had negative non-invasive mediastinal staging (3.7%) and were incidentally discovered. The most frequently affected lymph node station was 7 in 22 patients (37%), followed by 5,6 in 18 (31%). Mediastinoscopy found positive lymph nodes in 3 of 16 patients (19%) in which it was performed. Overall 5-year survival for pT1 N2 incidentally discovered during mediastinal lymph node dissection at the time of lung resection was 46% (95% confidence interval, 31% to 68%). Conclusions: True pT1 NSCLC harbors a relatively low rate of N2 disease. The rate of occult N2 disease not observed on noninvasive preoperative mediastinal staging is even lower. For patients with T1 NSCLC and negative mediastinal imaging, routine mediastinoscopy results in a low yield of occult N2 disease discovery.