Proposed Ninth Edition TNM Staging System for Lung Cancer: Guide for Radiologists

Lung cancer continues to be the primary cause of cancer-related deaths globally. Precise staging is imperative for the development of successful treatment approaches and improvement of patient outcomes. Traditionally, lung cancer staging has depended on the TNM staging system, and the International Association for the Study of Lung Cancer (IASLC) has recently recommended modifications. The updated classification for the ninth edition of the TNM staging system (TNM-9), slated to take effect in January 2025, is derived from a thorough analysis of a newly established large international database of lung cancer cases compiled by the IASLC. Proposed changes in TNM-9 include the following: (a) The mediastinal nodal category (N2) was split into single-station (N2a) and multiple-station (N2b) subcategories, and (b) multiple extrathoracic metastatic lesions (M1c) were split into single organ system (M1c1) and multiple organ systems (M1c2) subcategories. Considering these revisions, adjustments have been made to the established stage groups. In terms of pathologic nodal staging, patients in the post-neoadjuvant ypN category demonstrated worse prognosis than those in the similar non-neoadjuvant pN category. Understanding the fundamental changes introduced in TNM-9 enables radiologists to precisely determine the clinical stage of lung cancer and enhance therapeutic approaches.