Features of the TNM-9 classification for lung cancer and integration of TNM-8 limitations

Abstract

Relevance: Lung cancer ranks among the leading causes of morbidity and mortality in oncological diseases both in Kazakhstan and worldwide. Accurate tumor staging is crucial for choosing patient management strategies, considering the continuously advancing diagnostic and treatment methods. The 8th edition of the Tumor-Node-Metastasis (TNM) classification, introduced in 2017, brought significant changes to the staging approach, thereby improving its precision. However, accumulated data have demonstrated the need for further refinement, particularly in assessing mediastinal lymph nodes and systemic metastasis. Therefore, the 9th edition of TNM came into force on January 1, 2025. It includes important updates that require adaptation in radiological practice.
The study aimed to compare the 8th and 9th editions of the TNM classification in lung cancer and identify key changes to improve staging accuracy and facilitate multidisciplinary treatment planning.
Methods: This study conducted a structured review of the changes introduced in TNM-9 compared to TNM-8, with a focus on interpreting the N and M categories. The analysis utilized clinical guidelines from the International Association for the Study of Lung Cancer (IASLC) and recent publications reflecting current approaches to tumor staging.
Results: In the TNM-9 classification, the N and M categories were refined by introducing new subcategories, N2a/N2b and M1c1/ M1c2. The staging of several combinations of T and N categories was also revised. Particular emphasis was placed on the need for more detailed anatomical characterization of lymph nodes and the systemic nature of metastases.
Conclusion: Understanding the new provisions of TNM-9 is essential for accurate stage assessment, improving communication during multidisciplinary tumor boards, and optimizing therapeutic decision-making.