Significance of accurate hilar and intrapulmonary lymph node examination and prognostication in stage IA-IIA non-small cell lung cancer, a retrospective cohort study

Background: The examination of lymph nodes (LNs) plays an important role in the nodal staging of non-small cell lung cancer (NSCLC). For patients without LN metastasis, the main role of thorough LN examination is accurate staging, which weakens the effect of staging migration. To date, the role of hilar and intrapulmonary (N1) station LNs has not been fully appreciated. In this study, we aimed to confirm the significance of N1 LNs in long-term survival for stage IA-IIA NSCLC patients and to find the minimum number of LN to examine.

Methods: The data of patients who underwent radical lobectomy and were confirmed as having non-metastatic LNs from January 2008 to March 2018 were retrospectively screened. Pathology records were reviewed for the number of LNs examined. The Kaplan-Meier method and Cox regression model were used to identify survival and prognostic factors.

Results: The median number of resected N1 LNs was 8. The number of patients with 0-2 N1 LNs, 3-5 N1 LNs, 6-8 N1 LNs, 9-11 N1 LNs, and more than 11 N1 LNs examined was 181, 425, 477, 414, and 531, respectively. Sex (P = 0.004), age (P < 0.001), tumor size (P = 0.004), differentiation degree (P = 0.001), and number of N1 LNs examined (P = 0.008) were independent prognostic factors of overall survival. Gender (P = 0.006), age (P = 0.031), tumor size (P = 0.001), differentiation degree (P = 0.001), vascular invasion (P = 0.034), and number of N1 LNs examined (P = 0.007) were independent prognostic factors of disease-free survival. Compared with patients with 0-5 N1 LNs examined, patients with more than 5 N1 LNs examined had better OS (P = 0.015) and had better DFS (P = 0.015) if only a landmark 5-year follow-up was performed.

Conclusion: Increasing the number of N1 LN examination might improve the long-term survival of T1-2N0 NSCLC patients. These data indicate that at least 6 N1 nodes examined is an essential part in surgical and pathological management but cannot prove this. This finding should be confirmed in a large, prospective randomized clinical study.