A New N2 Descriptor for Resectable Non-Small Cell Lung Cancer: The Classification Based on Skip Metastasis and the Number of N2 Station Involvement.

Abstract

Patients with non-small cell lung cancer (NSCLC) are a heterogeneous group with varied patterns of disease. The skip mediastinal lymph node metastasis is quite frequent and a prognostic factor for patients with N2 lung cancer. The aim of this study is to assess the clinical significance and prognostic value of a new N2 descriptor based on skip N2 disease and ninth edition N2 classification. A retrospective review of 533 patients with stage pN2 NSCLC was undertaken. Patients were finally classified into three categories (skip N2a, skip N2b/nonskip N2a, and nonskip N2b). The clinic characteristics, survival outcomes, and metastasis pattern were analyzed among groups. Significant prognostic differences were found between patients of subdivided N2 descriptor (skip N2a vs. skip N2b/nonskip N2a and p < 0.001 for both OS and DFS and skip N2b/nonskip N2a vs. nonskip N2b, p = 0.037 for OS and p = 0.029 for DFS). Better prognostic value in predicting survival, including a smaller Akaike Information Criterion value and a higher Harrell C-index, was observed for the new N2 descriptor relative to the ninth edition N2 classification. Skip patients had better survival outcomes and different lymph node metastasis pattern compared with nonskip patients. When compared to the ninth N2 classification, the new N2 descriptor could be a more reliable and accurate prognostic determinant, which is worth considering in the revision of the current tumor, node, and metastasis (TNM) staging system.