Introduction: Lymph node involvement is one of the most important prognostic factors in cancer patients. It is categorized based on the anatomic extent, but differences in node involvement patterns are not incorporated in the tumor, node, metastasis classification. Squamous cell carcinoma more frequently arises in the central airway and invades adjacent lymph nodes directly than the other histologic types. The purpose of this study was to evaluate the prognostic impact of lymph node involvement patterns in pulmonary pN1 SCC patients.
Methods: We reviewed 120 consecutive patients with completely resected pN1 squamous cell carcinoma and classified them into two groups based on node involvement pattern: direct (all metastatic N1 nodes involved directly by the main tumor) and separate (one or more metastatic N1 nodes not directly involved by the main tumor) N1 groups. To compare the survival probability, 302 pN0 patients and 59 pN2 patients were also investigated.
Results: Univariate and multivariate analyses showed that the N1 node involvement pattern significantly associated with patient prognosis. The direct N1 group resulted in a much better 5-year overall survival rate of 67.7% compared with 32.4% for the separate N1 group (p < 0.01). The direct N1 group survival curve almost overlapped with the pN0 curve (p = 0.68), whereas the separate N1 group curve overlapped with the pN2 curve (p = 0.91).
Conclusions: Direct N1 metastatic cases are highly curable, similar to pN0 patients. In contrast, separate N1 metastatic cases are destined to poor prognosis similar to pN2 patients.