External validation of the eighth edition of the TNM classification for lung cancer in 3,611 surgically treated patients at a single institution

Background: A new revision of the tumor, node, metastasis (TNM) classification for lung cancer has been proposed by the International Association for the Study of Lung Cancer (IASLC), but external validation for it is required. This study aimed to evaluate stage groupings in the 8th edition of the TNM classification in an independent Chinese cohort. Methods: We retrospectively analyzed 3,611 patients who were diagnosed as stage I to IV non-small cell lung cancer (NSCLC) and who received surgical treatment at our institute in China between October 2009 and August 2017. Long-rank tests were used to compare survival between two adjacent stage groups. Results: Based on the 8th edition of the TNM classification, differences between every 2 adjacent stage groups were found to be significant except between Ia1 and Ia2 (P=0.062), and between IIIc and IVa (P=0.063). Significant differences were found between every 2 adjacent categories stratified by the T and N descriptors. Additionally, significant differences were found between M0 and M1a (P<0.001), while no significant difference was observed between M1a and M1b (P=0.092). Conclusions: Our study provides an external validation of the stage groupings in the 8th edition of the TNM staging system in surgically treated Chinese patients with NSCLC.