Recommended changes for the 8th edition of the TNM classification for lung cancer-the findings of a single-institution evaluation

Background To evaluate the efficacy of the nodal descriptors and subgroups proposed by International Association for the Study of Lung Cancer (IASLC) in the 8th edition of the TNM classification system and to provide references for future editions. Methods A total of 3,177 patients with non-small cell lung cancer at the Beijing Cancer Hospital were classified based on the following three methods: (I) the N descriptors in the 8th edition of the TNM classification system: N0, N1, N2, and N3; (II) the IASLC-proposed N subgroups: N1a, N1b, N2a1, N2a2, and N2b; (III) our more extensive division method: N1a, N1b, N1c, N2a1, N2a2, N2b1, N2b2, N2c, N3a, and N3b. Five-year survival analysis was performed using the Kaplan-Meier method, and differences between subgroups were evaluated using the log-rank test. Results (I) A significant survival difference was found between each adjacent N descriptor; (II) the difference between each adjacent subgroup N descriptor was significant, but the difference between N1b and N2a1 was not; (III) in our proposed method, a significant difference was found between all the subgroups apart from N2a2 and N2b1, N2b1 and N2b2, N2c and N3a, and N3a and N3b. Conclusions The N descriptors in the 8th edition of the tumor, node, and metastasis (TNM) classification system are consistent with our data. Although our more extensive division method could distinguish between patients at different stages, its implementation is complicated; thus, we recommend the implementation of the IASLC-proposed subgroups with the addition of the N1b and N2a1 groups.