The eighth TNM classification system for lung cancer: A consideration based on the degree of pleural invasion and involved neighboring structures.

OBJECTIVES

The eighth tumor-node-metastasis (TNM) classification system for lung cancer has been used since January 2017 and must be applied to an individual institution's database.

METHODS

We analyzed pathological stage data of 2756 patients who underwent resection of non-small-cell lung cancer, particularly in terms of the degree of visceral pleural invasion and involved neighboring structures.

RESULTS

Few patients had stage IIA disease (103, 4%); stratification between stages IB and IIA was insufficient (p = 0.129). When T2a tumors were divided into PL1 and PL2 subgroups based on the degree of pleural invasion, there was a significant prognostic difference between the subgroups (p < 0.001). By incorporating T2a tumors with PL2 (T2a-PL2) into the T2b category, modified stages IB, IIA (234, 8%), and IIB were well stratified (IB vs. IIA, p < 0.001; IIA vs. IIB, p = 0.011). Focusing on T3 tumors with PL3 (T3-PL3) invading neighboring structures, multivariate analysis for surveying pT3N0-2M0 tumors revealed that completeness of resection (p = 0.002), implementation of any postoperative therapies (p = 0.003), and subcategorization of whether only the pleura was infiltrated or other deeper structures were also invaded (p = 0.024) were significant and crucial predictors. N2 disease showed worse outcome than N0-1 diseases, with marginal difference (p = 0.054).

CONCLUSION

T2a-PL2 tumors could be categorized into a worse prognostic T2b category. For T3-PL3 tumors involving resectable neighboring organs, subcategorization of whether there is only pleura infiltration (T3a) or other deeper structure invasion (T3b) could be a practical consideration.