P1.17-05 What Is the Optimal Number of Examined Lymph Node in Stage IA Non-Small Cell Lung Cancer?

Abstract

1. To find out the optimal number of examined lymph nodes (ELNs) in stage IA non-small cell lung cancer (NSCLC). 2.To figure out whether there was a turning point beyond which ELNs might have adverse effects on survival. Using the Surveillance, Epidemiology, and End Results registry (SEER) database, we selected all NSCLC patients diagnosed with stage IA (T1N0M0) from 1995 to 2015. Cases from 1995 to 2005 were as analytical data set (group 1) and those from 2006-2015 as validation data set (group 2). The overall survival (OS) of patients with different ELNs was compared statistically by SPSS. The optimal cut point of ELNs was calculated by X-Tile and verified by univariable and multivariable analyses. Propensity score matching (PSM) was done by R software 3.5.2. In total, we extracted 57481 stage IA NSCLC patients (group 1, n = 20814; group 2, n = 36667). The PSM of Group 1 and Group 2 were balanced based on sex, age and race. In both groups, we divided patients into 3 subgroups, recorded as ELN = 0, 1≤ ELNs < n and ELNs≥ n. ELN = 0 had the highest risk of death in each subgroup (all p < 0.001). From n = 6 to n = 16, OS was significantly different between 1 ≤ ELNs < n, and ELNs ≥ n. But from n = 17 to n = 30, OS was the same between 1 ≤ ELNs < n and ELNs ≥ n. When dividing patients into ELNs = 0, 1-2, 3-5, 6-9, 10-29, ≥ 30, serial improvement in OS was seen with increasing ELNs, up to ELNs = 6-9, and beyond which there was little further incremental survival benefit. The survival curve of ELNs ≥ 30 even had an obvious trend to drop down. For stage IA NSCLC, we suggested resecting 6-9 LNs was enough, and no more than 16 LNs. More than 16 ELNs did not improve survival and more than 30 ELNs might have a detrimental effect on survival.