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

Recent evidence suggests that postoperative adjuvant radiotherapy (PORT) may enhance survival outcomes in patients with pN2 non-small cell lung cancer (NSCLC), particularly when analyzed through examined lymph nodes (ELNs) and lymph node ratio (LNR). This multicenter retrospective cohort study used data from the SEER-17 registry (2015–2019) to investigate the impact of ELNs and LNR on PORT efficacy in pN2 NSCLC patients. The analysis included 1,875 patients who underwent surgery and lymph node biopsy, excluding those with incomplete data. Statistical evaluations, including Cox proportional hazards models and X-tile software for LNR categorization, revealed that PORT significantly improved overall survival, with a 22% higher mortality rate in the non-PORT group (HR =1.22, 95% CI: 1.02–1.46, P=0.03) and up to 31% higher in fully adjusted models (HR =1.31, 95% CI: 1.09–1.58, P=0.004). PORT demonstrated particular effectiveness in patients with ELNs <10, especially when LNR ≤0.2 (HR =4.15, P=0.03) or LNR ≥0.53 (HR =1.83, P=0.01), findings supported by Kaplan–Meier survival curves. These results suggest that ELNs and LNR are valuable for identifying pN2 NSCLC patients who may derive significant survival benefits from PORT.