Prognostic significance of the pattern of pathological N1 lymph node metastases for non-small cell lung cancer

Background: In patients with non-small cell lung cancer (NSCLC) the pathologic lymph node status N1 is a heterogeneous entity, and different forms of lymph node involvement may represent different prognoses. For methodological reasons, the 8th edition of the TNM staging system for NSCLC makes no official changes to the N descriptor. However, there is evidence that different subforms of N1 disease are associated with different prognoses, and it is now recommended that clinicians record the number of affected lymph nodes and nodal stations for further analyses. In this investigation we sought to determine whether patients with different levels and types of N1 lymph node involvement had significantly different 5-year survival rates. Methods: We retrospectively identified 90 patients with NSCLC (61 men, 29 women), who were treated between 2008 and 2012 and found to have pathologic N1 lymph node involvement and tumor sizes corresponding to T1 or T2. All patients were treated in curative intent with surgical lung resection and systematic mediastinal and hilar lymph node dissection. Results: The overall 5-year survival rate was 56.3%. In the univariate analysis, lower tumor stage and tumor histology other than large-cell carcinoma were significantly associated with better long-term survival. Patients with solitary lymph node metastases also had longer disease-free survival than those with multiple nodal metastases. In the multivariate analysis, large-cell carcinoma and Union for International Cancer Control (UICC) stage IIB were independently associated with worse survival, while pneumonectomy, compared to lobar or sublobar resection, was independently associated with better survival. Conclusions: Although we did not observe significant prognostic differences between N1 subcategories within our patient population, other analyses may yield different results. Therefore, these data highlight the need for large, well-designed multicenter studies to confirm the clinical significance of N1 subcategories.