Endocrinol Metab.  2020 Mar;35(1):149-156. 10.3803/EnM.2020.35.1.149.

Modification of the Tumor-Node-Metastasis Staging System for Differentiated Thyroid Carcinoma by Considering Extra-Thyroidal Extension and Lateral Cervical Lymph Node Metastasis

• Kim M
• Kim WG
• Jeon MJ
• Kim HK
• Yi HS
• Kim ES
• Kim BH
• Kim WB
• Shong YK
• Kang HC
• Kim TY

• KMID: 2471731
• DOI: http://doi.org/10.3803/EnM.2020.35.1.149

Abstract

BACKGROUND
Concerns have arisen about the classification of extra-thyroidal extension (ETE) and lateral cervical lymph node metastasis (N1b) in the 8th edition of the tumor-node-metastasis staging system (TNM-8). This study evaluated the prognostic validity of a modified-TNM staging system, focusing on ETE and N1b, in differentiated thyroid carcinoma (DTC) patients.
METHODS
This multicenter retrospective cohort study included 4,878 DTC patients from five tertiary hospitals. In the modified-TNM, T3b in TNM-8 was down-staged to T2, and stage II was subdivided into stages IIA and IIB. Older patients with N1b were reclassified as stage IIB.
RESULTS
The modified-TNM resulted in staging migration in 540 patients (11%) classified as stage II according to the TNM-8, with 75 (14%), 381 (71%), and 84 patients (16%) classified as stages I, IIA, and IIB, respectively. The 10-year disease-specific survival (DSS) rates in patients classified as stages I, II, III, and IV by TNM-8 were 99.8%, 95.9%, 81.0%, and 41.6%, respectively. The DSS rates of patients classified as stages I, IIA, IIB, III, and IV according to the modified-TNM were 99.8%, 96.4%, 93.3%, 81.0%, and 41.6%, respectively. DSS curves between stages on TNM-8 (P<0.001) and modified-TNM (P<0.001) differed significantly, but the modified-TNM discriminated better than TNM-8. The proportions of variation explained values of TNM-8 and modified-TNM were 6.3% and 6.5%, respectively.
CONCLUSION
Modification of the TNM staging system focusing on ETE and N1b could improve the prediction of DSS in patients with DTC. Further researches are needed to validate the prognostic accuracy of this modified-TNM staging system.

Keyword

Lymph nodes; Mortality; Neoplasm staging; Thyroid neoplasms

MeSH Terms

Classification
Cohort Studies
Humans
Lymph Nodes*
Mortality
Neoplasm Metastasis*
Neoplasm Staging
Retrospective Studies
Tertiary Care Centers
Thyroid Gland*
Thyroid Neoplasms*

Figure

• 

  Fig. 1 Distribution of patients according to (A) T classifications and (B) tumor-node-metastasis (TNM) stages, as determined by the 8th edition of the TNM staging system (TNM-8) and the modified-TNM staging system.

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  Fig. 2 Kaplan-Meier analysis of disease-specific survival (DSS) in patients with differentiated thyroid carcinoma classified according to (A) the 8th edition of the tumor-node-metastasis (TNM) staging system (TNM-8) and (B) the modified-TNM staging system.

• 

  Fig. 3 Kaplan-Meier analysis of disease-specific survival (DSS) in patients who showed (A) stage migration after applying the modified-tumor-node-metastasis (TNM) staging system and (B) patients classified as stages IIA and IIB according to the modified-TNM. TNM-8, the 8th edition of the TNM staging system.

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