Risk analyses of N2 lymph-node metastases in patients with T1 non-small cell lung cancer: a multi-center real-world observational study in China

Purpose N2 lymph-node metastases occur in approximately 6-17% of the patients with T1-2 non-small cell lung cancer (NSCLC). However, the clinical characteristics of N2 patients are not fully understood. Methods This retrospective, multi-center analysis included T1 NSCLC patients receiving surgical resection during a period from Jan 2nd, 2014 to Dec 27th, 2017. The diagnosis was pathologically verified in all cases. Univariate and multivariate logistic regression analyses were conducted to analyze the factors that are associated with pN2 lymph-node metastases. Results A total of 10,885 patients (48.4% men; 84.7% adenocarcinoma) were included in the analysis. The mean age was 59.0 +/- 9.9 years. The mean tumor size was 1.8 +/- 0.8 cm. Of the patients, 3260 (29.9%) were smokers or ex-smokers. Lymph-node metastases were verified in 1808 (16.6%) patients, and 1167 (10.7%) patients had N2 lymph-node metastases. The multivariate analyses indicated that larger tumor size, lower differentiation, CEA level >= 5 ng/mL, vascular invasion (+), and pleural involvement (+) were associated with higher percentages of N2 lymph-node metastases (p < 0.001 for all). Conclusions This study demonstrated the significant association between N2 lymph-node metastases and tumor size and differentiation, CEA levels, and status of vascular invasion and pleural involvement.