Introduction to the ninth edition TNM staging of non-small cell lung cancer: A surgical perspective

PurposeThe ninth TNM staging of non-small-cell lung cancer (NSCLC) was introduced in 2023 to replace the eighth edition that had been in use since 2017. It provides a standardised universal language to discuss management of NSCLC patients. Outcomes across different patient populations can be better evaluated and this process is undertaken by the International Association for the Study of Lung Cancer Lung Cancer Staging Project team to further refine the staging classification past and present.Changes in descriptorsThere is no change to the size-based T-descriptors. Mediastinal nodal N-descriptors followed previous definitions but are now subdivided into N2a and N2b depending on single or multiple nodal stations involvement respectively. M1c M-descriptors that described multiple extra-thoracic metastases were also subclassified into single (M1c1) or multiple (M1c2) organ system involvement.Changes in stagingMajor revisions were made to stage 2 and 3 disease. Previous T1N1M0 disease is downstaged from stage 2B to 2A. T1N2aM0 disease is now downstaged to 2B whilst T1N2bM0 remained as stage 3A. Previous T2N2M0 and T3N2M0 disease were staged 3A and 3B respectively. Under the new classification, T2N2aM0 (unchanged) and T3N2aM0 (downstaged) are now stage 3A whilst T2N2bM0 (upstaged) and T3N2bM0 (unchanged) are now stage 3B.ConclusionThe ninth edition NSCLC TNM staging is now in place. It is important to be familiar with it to allow effective communication between surgical and medical oncologists to optimise patient care. It is also pertinent to start collecting and maintaining databases using the revised staging to help us further improve treatment in lung cancer patients.