The IASLC 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 tumor, node, metastasis (TNM) staging system. The N categories for lung cancer have remained unchanged since the 4th 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 (IASLC) database necessary for the 9th edition TNM staging system, members of the N-Descriptors Subcommittee of the IASLC 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 anatomic location of lymph node metastasis. We reviewed the literature focusing on non-small cell lung cancer (NSCLC) to stimulate dialogue and mutual understanding among subcommittee members engaged in developing the 9th 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.