Removing different number of regional lymph nodes affects survival outcomes of operable patients at stage IIA non-small cell lung cancer (according to the 8th edition staging)

BACKGROUND: Surgery combined with chemotherapy (CT) is the best treatment for tumor patients at stage I to IIIA. But there are only few studies specifically evaluated the survival benefits of removing different number of regional lymph nodes (RLNs) for patients with stage IIA non-small cell lung cancer (NSCLC). The objective of this study is to discuss the effect of removing different number of RLNs on survival outcomes in operable patients at stage IIA NSCLC. METHODS: Through the use of the Surveillance, Epidemiology, and End Results (SEER) registry, satisfactory patients at stage IIA NSCLC, who had complete clinical information from 2004 to 2015, were identified. Lung cancer-specific survival (LCSS) and overall survival (OS) were compared by the Kaplan-Meier analysis and Cox regression analyses to determine the impact of the confounding factors on the survival outcomes. LCSS and OS as the primary endpoints were compared among patients with different number of RLNs removed. RESULTS: A total of 3,362 patients at stage IIA NSCLC met our criteria, including 173 (5.1%), 486 (14.5%), 2,703 (80.4%) patients without RLNs removed, with 1 to 3 RLNs removed and with greater than or equal to 4 RLNs removed, respectively. Kaplan-Meier survival analyses and Univariate Cox regression analyses revealed that there was a statistically significant difference on survival curve (log rank P<0.001) among the stage IIA NSCLC patients with different number of RLNs removed. Furthermore, multivariable Cox regression analyses on LCSS showed that the hazard ratio (HR) and 95% confidence interval (95% CI) of the 1 to 3 RLNs removed group and greater than or equal to 4 RLNs removed group were 0.622 (0.484–0.800, P<0.001) and 0.545 (0.437–0.680, P<0.001), respectively, compared to without any RLNs removed group. CONCLUSIONS: This study illustrated that removing different number of RLNs can affect survival outcomes of operable patients at stage IIA NSCLC. Whether more radical lymphadenectomy is beneficial to patients at stage IIA NSCLC still needs to be researched.