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A single-center external validation and refinement of the 9th TNM staging system for thymic epithelial tumors: a
Ke Zhao1, Xiaoyun Zhou1, Lei Liu1
1Department of Thoracic Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China.
Objective:
This study aimed to perform a single-center external validation of the recently adopted 9th edition TNM staging system for thymic epithelial tumors (TETs) and to propose a refined scheme addressing its prognostic stratification anomalies.
Methods:
We conducted a retrospective cohort study of 540 patients with TETs treated at a single center from 2015 to 2021. All cases were rigorously re-staged according to 9th edition TNM criteria. The prognostic discrimination for overall survival (OS) and progression-free survival (PFS) of 9th edition TNM system was evaluated. Based on identified anomalies, a refined staging scheme was proposed.
Results:
The 9th edition TNM system demonstrated overall prognostic capability. However, significant stratification anomalies were observed: stage IIIA patients had paradoxically better OS and PFS than stage II patients, and the long-term survival curve of stage IIIB crossed below that of stage IV. Based on the extent of anatomical invasion, surgical complexity, and survival differences, we propose: (1) downgrading left brachiocephalic vein invasion to T2; (2) merging other T3/T4 lesions into a new T3 category (overall stage IIIA); (3) defining TanyN1M0 as stage IIIB; and (4) defining TanyN2M0 as stage IVA. Application of this refined scheme resulted in statistically significant, monotonically deteriorating trends for both OS and PFS across successive stages (P < 0.001), with markedly improved logical consistency.
Conclusion:
This single-center large-scale external validation reveals significant prognostic paradoxes in the 9th edition TNM system for TETs. The proposed refinement scheme effectively optimizes logical consistency and prognostic discrimination, offering potential implications for perioperative therapy planning.
