Proposal of new nodal classifications for non-small-cell lung cancer based on the number and ratio of metastatic lymph nodes

Abstract

The study aimed to evaluate the effectiveness of two new nodal classifications based on the number of metastatic lymph nodes (LNs) or ratio of metastatic to examined LNs (LNR) in making a prognosis, compared with the current nodal classification based on the location of metastatic LNs. We analyzed 651 non-small-cell lung cancer patients who had undergone complete resection with the removal of more than five LNs between 1986 and 2003, excluding preoperative treatment cases, and a Tis, T4, N3, and M1 status, along with limited resection and operative death cases. The cutoff numbers for each category in the two new nodal classifications (number of metastatic LNs (nN0-2): 0, 1-2, and >3, and LNR (rN0-2): 0, 1-12, and >12%) were defined so that the numbers corresponded with paired categories within the current nodal classification. The 5-year survival rate was 75.4% for patients with the N0 categories in all three classifications. The 5-year survival rates for patients with N1 and N2 categories were 52.2% and 42.6% according to the current nodal classification, 54.3% and 39.8% according to the number of metastatic LNs, and 58.8% and 35.0% according to the LNR, respectively. Although all three nodal classifications were independent prognostic factors along with the age and pathological T status, when the three nodal classifications were entered into multivariate analysis individually, the hazard ratio of rN2 was the highest, at 3.15, followed by that of nN2 at 2.96. The LNR followed by the number of metastatic LNs may be more effective prognostic indicators than the current nodal classification based on the location of metastatic LNs. For the future revision, the number of metastatic LNs and LNR should be evaluated as indicators for the nodal classification of lung cancer.