Combining node location and node ratio as a prognostic factor for surgical resected non-small cell lung cancer: a population-based study

Background In the TNM system only the anatomic location is used to define nodal status. In this study we aim to evaluate the effectiveness of combining the location and ratio of metastatic lymph node (pN-NR) for the prognosis of non-small cell lung cancer (NSCLC). Methods Patients with pN1/pN2 NSCLC were retrieved from the SEER database. The optimal cut point of NR was determined with the maximal selecting test. All patients were divided into 4 categories with combination of pN (pN1 or pN2) and NR (low or high). The pN-NR was investigated as a predictor of overall survival (OS) and cause-specific survival (CSS) using Cox regression models. Survival curves were plotted using the Kaplan-Meier method and the difference was compared with log-rank test. Results A total of 12,170 patients were enrolled. The optimal cut point of NR was 0.3. Patients were divided into 4 groups: pN1-NR <0.3, pN1-NR ≥0.3, pN2-NR <0.3 and pN2-NR ≥0.3. The pN-NR was an independent prognostic factor for survival. Compared with pN1-NR <0.3, the hazard ratio of OS was 1.405 (95% CI: 1.295-1.524), 1.183 (95% CI: 1.113-1257) and 1.717 (95% CI: 1.607-1.835) times higher for pN1-NR ≥0.3, pN2-NR <0.3 and pN2-NR ≥0.3 group, respectively. The survival curves of OS separated well between the 4 pN-NR groups, with 5-year OS 47.1% for pN1-NR <0.3, 43.0% for pN2-NR <0.3, 35.0% for pN1-NR ≥0.3 and 28.5% for pN2-NR ≥0.3, and the P value between neighboring curves was statistically significantly. The same trend was observed for CSS. Subgroup analysis revealed similar results except the pneumonectomy group. Conclusions pN-NR could be a good predictor for the prognosis of NSCLC.