The impact of station 4L lymph node dissection on short-term and long-term outcomes in non-small cell lung cancer

Objective The optimal extent of lymph node dissection (LND) remains controversial. We aimed to investigate whether the addition of station 4L lymph node dissection (S4L-LND) was beneficial for non-small cell lung cancer (NSCLC). Methods Data on 1040 left-sided NSCLC patients undergoing rigorous systematic LND were retrospectively reviewed. Multivariate logistic regression analysis determined risk factors of station 4L (S4L) nodal involvement to facilitate risk stratified analysis of the significance of S4L-LND. Propensity score matching (PSM) was conducted to reduce disparities of baseline characteristics between S4L-LND group and no-S4L-LND group. Recurrence-free survival (RFS), overall survival (OS), and postoperative complications were compared. Results S4L-LND was performed in 586 (56.3%) patients. The S4L nodal involvement rate was 15.5% (91/586). Aortopulmonary zone nodes involvement (P < 0.001), N1 nodes involvement (P < 0.001), and advanced T stage (P = 0.015) were independent risk factors of S4L nodal involvement. Patients with ≥ 2 risk factors of S4L nodal involvement were classified as high risk group, and the others were classified as low risk group. Among patients with negative aortopulmonary zone nodes and inferior mediastinal nodes (n = 425), only 28 (6.6%) patients had S4L involvement. After PSM, a total of 416 pairs were well matched. There was no significant survival difference between S4L-LND group and no-S4L-LND group (OS, P = 0.247; RFS, P = 0.569). When stratified by risk subgroup, S4L-LND group did not demonstrate superior survival than no-S4L-LND group in the high risk group (OS, P = 0.273; RFS, P = 0.754) or the low risk group (OS, P = 0.558; RFS, P = 0.319). S4L-LND group demonstrated significantly greater risk of postoperative complications than no-S4L-LND group (9.6% vs. 5.8%; P = 0.037). Conclusions S4L involvement was not rare and usually occurred with multiple nodal stations involvement. Routine dissection of aortopulmonary zone and inferior mediastinal nodes was sufficient to ensure staging accuracy. The addition of S4L-LND did not improve survival, but might increase the risk of postoperative complications.