The International Association for the Study of Lung Cancer Staging Project for Lung Cancer: Proposals for the Revision of the N Descriptors in the Forthcoming Ninth Edition of the TNM Classification for Lung Cancer.

INTRODUCTION: The accurate assessment of nodal (N) status is crucial to the management and prognostication of nonmetastatic NSCLC. We sought to determine whether the current N descriptors should be maintained or revised for the upcoming ninth edition of the international TNM lung cancer staging system. METHODS: Data were assembled by the International Association for the Study of Lung Cancer on patients with NSCLC, detailing both clinical and pathologic N status, with information about anatomical 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 reflect prognostically distinct groups. Furthermore, single-station N2 involvement (N2a) exhibited a 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 subdescriptors to N2 for single-station involvement (N2a) and multiple-station involvement (N2b).

The International Association for the Study of Lung Cancer Lung Cancer Staging Project: Overview of Challenges and Opportunities in Revising the Nodal Classification of Lung Cancer.

The status of lymph node involvement is a major component of the TNM staging system. The N categories for lung cancer have remained unchanged since the fourth edition of the TNM staging system, partly because of differences in nodal mapping nomenclature, partly because of insufficient details to verify possible alternative approaches for staging. In preparation for the rigorous analysis of the International Association for the Study of Lung Cancer database necessary for the ninth edition TNM staging system, members of the N-Descriptors Subcommittee of the International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee reviewed the evidence for alternative approaches to categorizing the extent of lymph node involvement with lung cancer, which is currently based solely on the anatomical location of lymph node metastasis. We reviewed the literature focusing on NSCLC to stimulate dialogue and mutual understanding among subcommittee members engaged in developing the ninth edition TNM staging system for lung cancer, which has been proposed for adoption by the American Joint Committee on Cancer and Union for International Cancer Control in 2024. The discussion of the range of possible revision options for the N categories, including the pros and cons of counting lymph nodes, lymph node stations, or lymph node zones, also provides transparency to the process, explaining why certain options may be discarded, others deferred for future consideration. Finally, we provide a preliminary discussion of the future directions that the N-Descriptors Subcommittee might consider for the 10th edition and beyond.