Association between smoking status and lymph node metastasis in Chinese patients with T1 non-small cell lung cancer: A real-world observational study

e20012 Background: Smoking and lymph node metastasis (LNM) are widely known to be the important risk factor for the induction and poor prognosis of non-small cell lung cancer (NSCLC) , respectively. However, the association between smoking status and LNM in Chinese patients with NSCLC is largely unknown. Methods: The patients with pathologically diagnosed T1 NSCLC undergoing surgical resection during 2014 to 2017 were retrospectively reviewed based on LinkDoc database. Patients without smoking status in the case records were excluded. Chi-square test was used for comparison between groups. Results: Of the 10,622 patients enrolled, 1,760 patients had LNM (16.6%). For smoking status, 3,260 (30.7%) patients were recorded with smoking history, with an average smoking index (SI) of 221.2. The incidence of LNM especially N2 station LNM in patients who ever smoked was significantly higher than those of never smokers in the enrolled population (22.8% vs. 13.6%, p < 0.001; N2: 14.3% vs. 9.1%, p < 0.001). Similarly, a larger proportion of current smokers than never smokers had LNM (24.0% vs. 13.6%, p < 0.001), and also more current smokers in only N2 station LNM (14.1% vs. 9.1%, p < 0.001). However, no statistically difference was observed in the proportion of patients with LNM particularly with N2 LNM between former and current smokers (24.0% vs. 22.8%, p = 0.401; N2: 14.1% vs. 14.3%, p = 0.887). Compared with non to light smoking (SI < = 400), patients with middle to heavy smoking ( > 400) were found to be more likely to develop LNM (N1/N2: 24.8% vs. 14.6%, p < 0.001; N2: 14.3% vs. 9.8%, p < 0.001). Conclusions: These findings from the real-world study indicated a close association between smoking both former and current and LNM especially N2 station LNM in patients with T1 NSCLC. [Table: see text]