Review of the Proposals in the Forthcoming 8th TNM Classification of Lung Cancer

Staging of lung cancer is a key factor for both prognostication and management of patients. Thus, there is a need for an accurate, uncomplicated, easily reproducible staging system. The database of the 8th TNM (T: Tumor, N: Node, M: Metastasis) classification is based on information gathered from 94,708 patients who received diagnoses of lung cancer between 1999 and 2010, originating from 35 sources in 16 countries. Data analysis was performed in 2013–2014 regarding proposals put forward for the 8th edition and was published in the Journal of Thoracic Oncology. It is thought that the 8th edition will be used in 2017. In this edition, tumor diameter is more important and each centimeter counts (T1a: ≤1 cm, T1b: >1 cm but ≤2 cm, T1c: >2 cm but ≤3 cm, T2a: >3 cm but ≤4 cm, T2b: >4 cm but ≤5 cm, T3: >5 cm but ≤7 cm, and T4: >7 cm). There are changes in some T descriptors such as main bronchus involvement (T2), total atelectasis/pneumonitis (T2), involvement of diaphragm (T4), and mediastinal pleural invasion (not used as T descriptor). Current N staging is still valid; however, there are clues for the importance of the abundance of nodal involvement. Three metastatic groups are defined: M1a (contralateral/bilateral tumor nodules, pleural/pericardial nodules or effusion), M1b (single metastatic lesion in one organ), and M1c (multiple metastasis in either single or multiple organs). More stage groupings demonstrating good prognostic categories are proposed. These changes do not have much implication on treatment. The proposed taxonomic changes do not affect therapeutic modalities. However, care should be taken to follow up for small pulmonary nodules.