[Impact of the extent of mediastinal lymph node dissection on postoperative survival in patients with cT1N0-1M0...

Objective: To investigate the impact of different extents of mediastinal lymph node dissection on postoperative survival in patients with cT1N0-1M0 non-small cell lung cancer (NSCLC). Methods: A single-center retrospective cohort study was conducted. A total of 639 patients with cT1N0-1M0 primary NSCLC who underwent curative-intent surgical resection at the Fourth Hospital of Hebei Medical University between January 2015 and December 2017 were consecutively enrolled. The cohort included 340 males and 299 females, with an age of (61.0±8.4) years (range: 31 to 79 years). Based on the extent of mediastinal lymph node dissection, patients were divided into three groups: the lobe-specific lymph node dissection group (n=72), the extended lymph node dissection group (n=228, beyond lobe-specific stations), and the limited lymph node dissection group (n=339, failed to cover lobe-specific stations). Subgroup analyses were stratified by tumor size (≤1 cm vs.>1 to 3 cm), pathological type (adenocarcinoma vs. non-adenocarcinoma), tumor location (peripheral vs. central), and pathological N stage (N0 vs. N1-2). The primary endpoint was overall survival. The Kaplan-Meier method was used to plot survival curves, and comparisons between groups were performed using the Log-rank test with Bonferroni correction for multiple comparisons (adjusted α=0.017). Independent prognostic factors were identified using the Cox proportional hazards regression model. Results: The follow-up time (M(IQR)) was 66.7 (25.9) months, and the overall 5-year survival rate was 82.1%. The 5-year survival rates in the extended, lobe-specific, and limited groups were 84.9%, 92.9%, and 77.9%, respectively, with a statistically significant difference among the three groups (P=0.004). Pairwise comparisons showed significant differences between the extended and limited groups (P=0.015) and between the lobe-specific and limited groups (P=0.008), but no significant difference between the extended and lobe-specific groups (P=0.181). Multivariate Cox regression analysis identified age, lymph node dissection pattern, T stage, and N stage as independent prognostic factors for postoperative survival (all P<0.05). Subgroup analyses revealed that in patients with tumor size >1 to 3 cm, lung adenocarcinoma, and peripheral-type lung cancer, lobe-specific lymph node dissection (including both the lobe-specific and extended groups) was associated with significantly better survival compared with limited dissection (all P<0.01). However, in patients with tumor size ≤1 cm, non-adenocarcinoma, and central-type lung cancer, no significant survival differences were observed among the three groups (all P>0.05). Conclusions: In curative-intent surgery for cT1N0-1M0 NSCLC, performing lobe-specific mediastinal lymph node dissection significantly improves postoperative survival compared with limited dissection. Further extension of lymph node dissection beyond the lobe-specific range does not confer additional survival benefit.