The prognostic value of lymph node ratio in patients with surgically resected stage I–III small-cell lung cancer: a propensity score matching analysis of the SEER database

Abstract OBJECTIVES Due to the lack of prospective studies, the role of the lymph node ratio (LNR) in small-cell lung cancer (SCLC) remains unknown. This study aimed to assess the prognostic effect of LNR in surgically resected stage I–III SCLC patients. METHODS Clinical data of stage I–III (excluding N3 and NX) SCLC patients diagnosed between 1998 and 2016 were extracted from the Surveillance, Epidemiology and End Results database. Patients were divided into low-risk and high-risk subsets based on the LNR cut-off value of 0.15 using X-tile software. Propensity score matching analysis was employed to reduce bias in baseline characteristics. Kaplan–Meier analysis was performed to determine the overall survival (OS) and lung cancer-specific survival (LCSS). Cox regression analysis was performed to evaluate the effects of multiple variables. RESULTS A total of 978 patients were identified, of whom 669 (68.40%) had LNR ≤0.15. Patients with LNR ≤0.15 showed better OS (P < 0.001) and LCSS (P < 0.001) both before and after propensity score matching. Multivariable analyses of the matched population confirmed LNR as an independent prognostic factor. Patients with LNR >0.15 showed poorer OS [hazard ratio (HR) 1.55, 95% confidence interval (CI) 1.09–2.19; P = 0.015] and LCSS (HR 1.65, 95% CI 1.13–2.43; P = 0.010). Subgroup analyses revealed that LNR ≤0.15 was associated with favourable OS (P = 0.009 and 0.197, respectively) and LCSS (P = 0.010 and 0.169, respectively) in N1 and N2 patients. CONCLUSIONS LNR was determined as an independent predictor for surgically resected stage I–III SCLC, indicating that higher LNR is associated with reduced survival. The predictive value of LNR should to be further validated in prospective studies.