Prognostic impact of node involvement pattern in pN1 non-small cell lung cancer patients

Introduction: We previously showed that squamous cell carcinoma (SCC) patients with directly involved N1 nodes resulted in outcomes significantly better than those with separately involved N1 nodes. The purpose of this study was to evaluate the prognostic effect of node involvement patterns in pN1 non-small cell lung cancer (NSCLC) patients, with special attention given to any differences between SCC and adenocarcinoma (AD). Methods: We reviewed 324 consecutive patients with completely resected pN1 NSCLC and classified them into two groups based on their node involvement patterns: directly or separately involved N1 groups. To compare survival rates, 1545 pN0 patients and 330 pN2 patients were also investigated. Results: Univariate and multivariate analyses showed that the node involvement pattern was significantly associated with pN1 NSCLC patient outcome. The directly involved N1 group had a much better 5-year overall survival rate of 60.1% compared with 45.0% for the separately involved N1 group. In SCC patients, the directly involved N1 group showed an overall survival similar to pN0 patients, whereas overall survival of the separately involved N1 group was identical to that of pN2 patients, and their survival rates were significantly different. In AD patients, however, the survival rates were marginally different between the directly and separately involved N1 groups, and they were intermediate between pN0 and pN2 patient survival rates. Conclusions: Node involvement patterns had significant prognostic effect in pN1 NSCLC patients. This effect was different between SCC and AD cases. The subclassification of N1 based on node involvement pattern is of significance for SCC patients but not for AD patients.