The Valuable Prognostic Impact of Regional Lymph Node Removed on Outcomes for IIIA N0 NSCLC Patients

Background: Regional lymph nodes (RLNs) removed combined with surgery is a standard option for patients at stage I to IIIA NSCLC. The objective of the study is to clarify the effect of removing different number of RLNs on survival outcomes for patients at stage IIIA N0 NSCLC. Methods: Patients at stage IIIA N0 NSCLC from 2004 to 2015 were identified from Surveillance, Epidemiology, and End Results (SEER) database. Prior propensity score method (PSM), survival time was compared among different number (0, 1-3 and ≥4) of RLNs removed groups. After PSM, lung cancer-specific survival (LCSS) and overall survival (OS) were compared. Kaplan-Meier analysis and Cox regression analyses were used to clarify the impact of the factors on the prognosis with hazard ratio (HR) and 95% confidence interval (CI). Results: A total of 11,583 patients at stage IIIA N0 NSCLC were included. Prior PSM, survival indicators including 1-year mortality rate, 5-year mortality rate, median survival time (MDST) and mean survival time (MST) from good to bad were all: ≥4, 1-3 and none RLNs removed group. After PSM, Kaplan-Meier survival analyses and univariate Cox regression analyses on OS and LCSS revealed a statistically significance on survival curve (P<0.001) between each two of the three groups (none, 1-3 and ≥4 RLNs removed group). Multivariable Cox regression analyses on OS and LCSS showed an independent association of RLNs removed with higher OS (HR, 0.275; 95% CI, 0.259-0.291; P<0.001) and LCSS (HR, 0.239; 95% CI, 0.224-0.256; P<0.001) compared with none RLN removed and no statistical difference with OS (HR, 1.118; 95% CI, 0.983-1.271; P=0.088) and LCSS (HR, 1.107; 95% CI, 0.954-1.284; P=0.179) between 1-3 RLNs removed and ≥4 RLNs removed. Conclusions: Removing RLNs was beneficial to survival outcomes of patients at stage IIIA N0 NSCLC. Compared with 1-3 RLNs removed, ≥4 RLNs removed could bring a better survival time but not an independent prognostic factor (P>0.05).