Background: Although preoperative radiotherapy (PORT) is a promising therapeutic option for stage III non-small cell lung cancer (NSCLC), the efficacy of this treatment remains controversial. The positive lymph node ratio (PLNR) is recognized as an independent prognostic factor for survival. However, no previous studies have focused on the association between PLNR and PORT in stage III NSCLC.
Methods: Data were collected from the Surveillance, Epidemiology and End Results (SEER) database, and all patients enrolled in this analysis were diagnosed during 2010-2015. The primary endpoint was overall survival (OS). Univariate and multivariate Cox regression analysis was used to identify factors associated with survival before and after case-control matching. PLNR was defined as the ratio of the number of positive lymph nodes to the total number of retrieved or examined lymph nodes. A cutoff value for PLNR was calculated using an X-tile model.
Results: Overall, 391 patients with PORT and 2814 patients without PORT were enrolled in this study. The cohort after 1:1 case-control matching included 322 patients who received PORT and 322 patients without PORT. PORT was not associated with a significant effect on OS (HR = 1.14; 95% CI: 0.91-1.43; P = 0.825). Multivariate Cox regression analysis showed that PLNR (P < 0.001) was independently associated with OS in patients with stage III NSCLC. An X-tile model was used to identify a cutoff value for PLNR: the risk of death was significantly lower in patients with PLNR ≤0.41 who received PORT than in those with PLNR >0.41 who received PORT (HR = 0.59; 95% CI: 0.38-0.91; P = 0.015).
Conclusion: PLNR may be a prognostic factor for survival in patients with stage III NSCLC who undergo PORT. Lower PLNR is a predictor of better OS and thus warrants further study.
Keywords: nomogram; non-small cell lung cancer (NSCLC); overall survival (OS); positive lymph node ratio (PLNR); preoperative radiotherapy (PORT).