Recommended optimal range for the count of examined lymph nodes and lymph node ratio for postoperative adjuvant radiotherapy in patients with pN2 non-small cell lung cancer: a multicenter retrospective cohort investigation.

Background: Recent evidence suggests that postoperative adjuvant radiotherapy (PORT) may enhance survival outcomes in patients with pN2 non-small cell lung cancer (NSCLC), particularly when evaluating through examined lymph nodes (ELNs) and lymph node ratio (LNR). This study aims to explore the impact of ELNs and LNR on the efficacy of postoperative radiotherapy in pN2 stage NSCLC patients through a multicenter retrospective cohort analysis, providing valuable insights for clinical treatment decisions.

Methods: Data were meticulously extracted from the Surveillance, Epidemiology, and End Results (SEER) 17 registry spanning 2015 to 2019. The study specifically targeted pN2 stage NSCLC patients who underwent surgical intervention and lymph node biopsy, involving an analysis of 1,875 patients while excluding those with incomplete data. The impact of PORT on overall survival (OS) was assessed, stratified by ELNs and LNR. Statistical analyses employed X-tile software to categorize LNR into three distinct groups, and Cox proportional hazard models were utilized to evaluate the influence of various factors on OS.

Results: The Cox proportional hazards model revealed a significant survival advantage associated with PORT, demonstrating a 22% higher mortality rate in the non-PORT group [hazard ratio (HR) =1.22, 95% confidence interval (CI): 1.02-1.46, P=0.03] and up to 31% higher in the fully adjusted model (HR =1.31, 95% CI: 1.09-1.58, P=0.004). PORT notably improved survival in patients with ELNs <10, particularly when LNR ≤0.2 (HR =4.15, P=0.03) and LNR ≥0.53 (HR =1.83, P=0.01). Kaplan-Meier survival curves corroborated these findings.

Conclusions: Our findings indicate that the number of ELNs and the LNR could serve as valuable criteria for selecting pN2 NSCLC patients who may benefit from PORT. PORT has been linked to improved survival outcomes in pN2 stage NSCLC, with a particular emphasis on its efficacy in patients with ELNs <10 and an LNR of ≤0.2.