Prognostic impact of lymph node ratio in patients with pT1–2N1M0 non-small cell lung cancer

BACKGROUND: This study evaluated the lymph node ratio (LNR) defined as the ratio of the number of metastatic lymph nodes to the number of dissected lymph nodes as a prognostic factor for survival in patients with pT1–2N1M0 non-small cell lung cancer (NSCLC). METHODS: We retrospectively reviewed 413 patients with pathologic T1–2N1M0 NSCLC after complete surgical resection and mediastinal LN dissection between January 2004 and December 2012. The cut-off value for LNR was determined using χ(2) tests, which were calculated using Cox proportional hazards regression model. Based on this model, the optimal cut-off value for LNR was 0.1. RESULTS: The study included 337 males and 76 females with a mean age of 62 years (range, 34–83 years). Patients with a high LNR (≥0.1) were more likely to be female and have more adenocarcinomas compared with patients with a low LNR (<0.1). The overall survival (OS) and disease-free survival (DFS) rates were significantly worse in the high LNR group than the low LNR group (OS, 55.4% vs. 69.8%, respectively P=0.003; DFS, 33.2% vs. 61.7%, P<0.001). In the multivariate analysis, a high LNR was associated with significantly worse OS [adjusted hazard ratio (aHR), 2.69; 95% confidence interval (CI), 1.74–4.17] and DFS (aHR, 2.41; 95% CI, 1.57–3.68). CONCLUSIONS: LNR is an independent prognostic factor for survival in patients with pT1–2N1M0 NSCLC. These findings may provide useful prognostic information to allow the selection of patients for more aggressive postoperative therapy or follow-up strategies.