Role of Skip Mediastinal Lymph Node Metastasis for Patients With Resectable Non-small-cell Lung Cancer: A Propensity Score Matching Analysis.

BACKGROUND: N2 disease represents a heterogeneous group of non-small-cell lung cancer (NSCLC) with varying 5-year overall survival (OS) rates. The skip N2 phenomenon is quite frequent, and its prognostic impact remains a matter of debate. The aim of this study is to further assess the clinical significance and prognostic value of skip N2 disease using propensity score matching.

PATIENTS AND METHODS: The study cohort included 437 patients with stage pN2 NSCLC who underwent resection from 2005 to 2011. Differences in clinicopathologic characteristics were identified in the overall cohort. The effect of skip N2 on OS was assessed, stratified by histology, tumor size, N2 involved stations, and T stage after propensity score matching.

RESULTS: A total of 130 patients had skip N2 diseases in our study. Skip N2 metastasis was associated with age, tumor size, histology, and number of involved N2 stations. Matching of 130 pairs of patients showed that skip N2 was associated with a significantly better 5-year OS rate when compared with non-skip N2 disease (42.7% vs. 25.3%; P = .004), and OS is significantly better in the patients with tumor size of ≤ 3 cm (P = .014) or patients with single N2 station involvement (P = .002). Skip N2 conferred a significantly better OS in stage IIIA (P = .026) and IIIB (P = .029) disease.

CONCLUSION: The presence of skip N2 metastasis was a good prognostic factor of resectable N2 disease. N2 disease may be classified into more subgroups in the revision of the current tumor-lymph node-metastasis (TNM) system.