Purpose: Our study was to evaluate the influence of positive lymph nodes ratio (PLNR) on survival for patients with pathological stage IIIA-N2 non-small cell lung cancer (NSCLC) after receiving postoperative radiotherapy (PORT).
Patients and methods: The chi-squared test was used to compare the patient baseline characteristics. Cox proportional hazard model was used to analyze the influence of different variables on overall survival (OS). X-tile model was applied to determine the cutoff values of PLNR. Kaplan–Meier method and log-rank test were used to compare survival differences. Based on different cutoff values of PLNR, Cox proportional hazard model was also used to analyze the influence factors on OS.
Results: Multivariate Cox regression analysis showed that PLNR (P =0.001) and PORT (HR=1.283; 95% CI 1.154–1.426; P <0.001) were significant independent prognostic factors for OS in patients with resected IIIA-N2 NSCLC. The X-tile model was used to screen three different cutoff values including PLNR≤20%, 20%40%. Based on these different cutoff values, we found that patients with PLNR≤20% receiving PORT have a better OS (P =0.007). Further multivariable analysis showed that PORT is an independent prognostic factor of OS only for patients with PLNR≤20% (HR=1.328; 95% CI 1.139–1.549; P <0.001).
Conclusion: PLNR≤20% may be a prognostic factor for patients with IIIA-N2 NSCLC receiving PORT.
Keywords: non-small cell lung cancer, postoperative radiotherapy, positive lymph node ratio, OS, prognosis, X-tile model