P1.13-008 Evaluation of Clinical Associated Factors for Lung Adenocarcinoma by TNM 8th Edition with Unexpected N2 disease

Among patients with lung adenocarcinoma, some of them diagnosed as clinical N0 (cN0) are staged as pathological N2(pN2; unexpected N2 disease). The aim of this study is to analyze preoperative factors of unexpected N2 disease. We retrospectively reviewed 361 cN0 lung adenocarcinoma patients who underwent curative resection between January 2005 to December 2016 in our institution. Patients were staged according to findings of computer tomography (CT), positron emission tomography (PET), and/or transbronchial needle aspiration (TBNA). We analyzed their clinical features, comparing pN0 group with pN2 group. Especially, we focused on the diameter of solid component by TNM classification 8th edition. There were 37 patients (10.2%) with unexpected N2 disease. Of the 37 patients, 10 patients (27.0%) had metastasis in Single-station N2 without N1 involvement (skip N2 disease), 14 patients (37.8%) had in Single-station N2 and 13 patients (35.1%) had in Multiple-station N2. There was no difference in the tumor size between pN0 and pN2 (p=0.100). However, the diameter of solid component was larger in pN2 than in pN0 (p<0.001), C/T ratio (p<0.001), maximum standard uptake value (p<0.001), and CEA (p=0.005) were higher in pN2 than in pN0. Multivariate logistic regression analysis identified the diameter of solid component and CEA as significant associated factors for unexpected N2 disease (p=0.006, p=0.01). The possibility of unexpected N2 disease increases with the larger diameter of solid component or higher CEA. Particularly, in order to discover unexpected N2 disease in lung adenocarcinoma, it is reasonable to evaluate T-factor by TNM classification 8th edition.