The prognostic impact of lymph node metastasis in patients with non-small cell lung cancer and distant organ metastasis

This study aimed to identify the prognostic value of lymph node metastasis in patients with non-small cell lung cancer (NSCLC) and distant organ metastasis. A total of 42,613 NSCLC patients with distant metastasis from the surveillance, epidemiology, and end results database between 2010 and 2013 were included for analysis. The proportion of N0 stage in M1a patients was significantly higher than that in M1b patients, 34.0% and 22.7% respectively (P < 0.001). Compared with N0 patients, patients had higher odds of experiencing multiorgan metastases (MOM) if they had higher N stage at diagnoses (P < 0.001). The Kaplan-Meier curves suggested both M1a and M1b groups patients at stage N0 had better survival than those at higher N stage (P < 0.001). Further analysis indicated that better survival was observed in N0 stage compared with N2 or N3 stage if patients had bone metastasis, brain metastasis, or MOM (P < 0.001, P < 0.001, and P = 0.002, respectively), but there was no significant difference in survival among each N stage patients with liver metastasis only. Cox regression analysis showed that compared with N0 patients, higher hazard for disease-specific mortality was observed for patients with higher N stage. Among NSCLC patients with distant organ metastasis, lymph node metastasis was associated with higher odds of experiencing MOM and a worse prognosis in terms of longer survival except patients with liver metastasis. Better understandings of the role of lymphatic metastasis in M1 NSCLC could help clinicians with better management of the disease.