Clinical Evaluation of T Component in the Ninth Edition TNM Classification of Thymic Epithelial Tumors

The optimal staging system for thymic epithelial tumors (TETs) remains controversial. This study aimed to evaluate the clinical utility of the T component in the latest ninth edition of the TNM staging system.

A retrospective analysis was performed on patients diagnosed with TETs at our center from January 2001 to December 2022. Recurrence-free survival (RFS) and overall survival (OS) were analyzed using Kaplan-Meier curves and Cox proportional hazards regression models. The predictive performance of the TNM staging systems was mainly assessed by the concordance index (C-index) and area under the receiver operating characteristic curve (AUC).

Ultimately, 545 patients with TETs were included. The ninth edition TNM staging system demonstrated superior discrimination compared to the eighth edition TNM staging in RFS outcomes, particularly for T1b versus T2 patients (HR = 3.58, p = 0.014). Prognostic accuracy metrics also favored the ninth edition, with higher AUC values (RFS: 0.83 vs. 0.824; OS: 0.726 vs. 0.685) and C-index values (RFS: 0.823 vs. 0.816; OS: 0.743 vs. 0.685).

The ninth edition TNM staging system provides enhanced prognostic accuracy for RFS in patients with TETs compared to the eighth edition, although both editions have limitations in predicting OS. Further studies are warranted to refine staging approaches and improve patient management in TETs.