The IASLC Lung Cancer Staging Project: Proposals for the Revision of the N Descriptors in the Forthcoming 9th Edition of the TNM Classification for Lung Cancer.

INTRODUCTION The accurate assessment of nodal (N) status is crucial to the management and prognostication of non-metastatic non-small cell lung cancer. We sought to determine whether the current N descriptors should be maintained or revised for the upcoming 9th edition of the international Tumor Node Metastasis (TNM) lung cancer staging system. METHODS Data was assembled by the International Association for the Study of Lung Cancer on patients with non-small cell lung cancer, detailing both clinical and pathologic N status, with information about anatomic location and individual station-level identification. Survival was calculated by the Kaplan-Meier method and prognostic groups were assessed by a Cox regression analysis. RESULTS Data for clinical N and pathologic N status were available in 45,032 and 35,009 patients, respectively. The current N0 to N3 descriptors for both clinical N and pathologic N categories demonstrated prognostically distinct groups. Furthermore, single station N2 involvement (N2a) demonstrated better prognosis than multistation N2 involvement (N2b) in both clinical and pathologic classifications, and the differences between all neighboring nodal subcategories were highly significant. The prognostic differences between N2a and N2b were robust and consistent across resection status, histologic type, T category, and geographic region. CONCLUSIONS The current N descriptors should be maintained, with the addition of new sub-descriptors to N2 for single station involvement (N2a) and multiple station involvement (N2b)