The Influence of Clinical T Factor on Predicting Pathologic N Factor in Resected Lung Cancer

Background: We investigated the utility of the clinical T factor of the 8th edition of the TNM classification, which newly defines the consolidation size of the tumor, as a valuable predictor of pathologic lymph node metastasis (pN+) and the prognosis.

Methods: We retrospectively reviewed 825 patients with surgically resected cN0 M0 non-small cell lung cancer of any T stage, focusing on the tumor's total size (7th edition) and consolidation size (8th edition) and examined pN+ and the prognosis.

Results: No pN+ cases in the 7th or 8th edition groups had a tumor size of less than 1 cm, and in those sized 1 to 3 cm, the frequency of pN+ in the 7th and 8th edition groups was 10.3% and 13.4%, respectively. The frequency of pN+ in tumors without ground glass opacity (GGO-) was 5.5-times higher than that of tumors with GGO (GGO+). The frequency of pN+ in the GGO+ 8th edition group was twice that in the GGO+ 7th edition group. The frequency of pN+ in the GGO- 7th edition group was 4-times higher than that of the GGO+ 7th edition group. A multivariate analysis revealed that total size exceeding 2 cm, consolidation size exceeding 2 cm, and GGO- were significant predictors of a pN+ status, indicating that a consolidation size of more than 2 cm was a stronger predictor than a total size of more than 2 cm.

Conclusions: A consolidation size of more than 2 cm and GGO- were predictors of pN+, and the clinical T factor of the 8th Edition was a stronger predictor of the pN+ status than that of the 7th edition.