Analysis of the relationship between the anatomical location of intrapulmonary metastatic lymph nodes and relapse risk and survival in patients with N1 non-small cell lung cancer

Abstract

Objective: To evaluate the relationship between the anatomical location of intrapulmonary metastatic lymph nodes and relapse risk and survival in patients with N1 non-small cell lung cancer(NSCLC). Methods: A retrospective analysis of the clinical and pathological data of 138 patients with completely resected N1 NSCLC was conducted. There were 79 males and 59 females, aged from 26 to 81 years with an average of (59±10) years. All of them were treated in the Department of Thoracic Surgery Ⅱ of Peking University Cancer Hospital between January 2007 and December 2015. Patients were stratified based on the 8th edition of the American Joint Committee on Cancer (AJCC) N1 classification and the modified pathological N1 classification strategy, respectively. According to modified pathological N1 classification strategy, which was defined based on the anatomical location of intrapulmonary metastatic lymph nodes, N1 nodes were subcategorized into the hilar (stations 10-11, mN1b) (n=36) and peripheral (stations 12-14, mN1a) (n=102) zones. The Kaplan-Meier curves were plotted to compare the relapse risk and survival analysis, disease-free survival (DFS), and overall survival (OS) were compared between the two staging methods through univariate and multivariate analysis to evaluate the effectiveness of the two classifications in stratifying patients with distinct risks of disease relapse and survival. Results: According to the modified N1 classification, the differences in 5-year DFS and OS between the subgroups (mN1a vs mN1b) were statistically significant(59.5% vs 35.7%; 81.2% vs 56.0%; both P<0.05). However, following the 8th edition of the AJCC N1 classification, no significant differences were found in DFS and OS between the subgroups (both P>0.05). Multivariate analysis showed that the modified N1 classification was an independent prognostic factor to DFS (HR=1.814, 95%CI: 1.005-3.275) and OS (HR=3.919, 95%CI: 1.918-8.009) (all P<0.05). However, the 8th edition of the AJCC N1 classification was not an independent prognostic factor to DFS (HR=1.360, 95%CI:0.767-2.412) or OS (HR=1.620, 95%CI:0.839-3.131) (both P>0.05) as revealed by multivariate analysis. Conclusions: The relapse risk and survival could be assessed effectively using the modified pathological N1 classification, which was defined and subcategorized based on the anatomical location of intrapulmonary metastatic lymph nodes for N1 NSCLC patients. The modified pathological N1 classification is superior to the 8th edition of the AJCC classification.