Characterization of Extracapsular Lymph Node Involvement and Its Clinicopathological Characteristics in Stage II-IIIA Lung Adenocarcinoma.

BACKGROUND: The prognostic impact and clinicopathological characteristics of extracapsular lymph node involvement (ECLNI) in patients with surgically resected lung adenocarcinoma (LUAD) remain unknown in the context of the eighth edition N classification. PATIENTS AND METHODS: We retrospectively reviewed 279 patients with stage II-IIIA LUAD who underwent lobectomy and lymphadenectomy. The correlations of ECLNI presence and clinicopathological profiles were analyzed. We also assessed the impact of ECLNI on the postoperative survival of pN1 and pN2 LUAD patients. RESULTS: ECLNI-positive status was more common in patients with high lymph node yield and in patients with multiple stations involved. The logistic regression model identified tumor spread through air spaces, micropapillary component, cribriform component, and nodal stage as predictive factors for ECLNI presence. LUAD patients with ECLNI presence had an increased risk of locoregional recurrence compared with those without (p < 0.001). Presence of ECLNI was confirmed as an independent risk factor for worse recurrence-free survival (RFS) (p < 0.001) and overall survival (OS) (p < 0.001) in the entire cohort. Among the 61 patients with ECLNI(+)pN2 disease, our analysis revealed that adjuvant radiation was a significant predictor of improved RFS and OS. In addition, ECLNI status provides additional precision in stratifying pN1 and pN2 patients with significantly different RFS and OS. CONCLUSIONS: Our data suggest that ECLNI remains a strong prognosticator of unfavorable OS and RFS for LUADs in the context of the eighth edition N classification. Adjuvant radiation should be actively considered for pN1b and pN2 LUAD patients with ECLNI presence.