An Analysis of The American Joint Committee on Cancer 8th Edition T Staging System for Papillary Thyroid Carcinoma.

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An Analysis of The American Joint Committee on Cancer 8th Edition T Staging System for Papillary Thyroid Carcinoma.

J Clin Endocrinol Metab. 2018 Apr 16;:

Authors: Tran B, Roshan D, Abraham E, Wang L, Garibotto N, Wykes J, Campbell P, Ebrahimi A

Abstract
Background: The American Joint Committee on Cancer (AJCC) removed microscopic extrathyroidal extension (m-ETE) from the 8th edition T staging for papillary thyroid carcinoma (PTC) based on increasing evidence that it is not an independent prognostic factor.
Objectives: We aimed to compare the prognostic performance of AJCC 7th (pT7) and 8th (pT8) edition T stage systems, particularly in patient's ≥55 years old without macroscopic ETE or distant metastases, in whom T classification impacts TNM stage.
Method: A retrospective analysis of disease-free survival (DFS) in 577 patients with PTC comparing pT8 versus pT7 using the Akaike information criterion (AIC), Harrell's C-index and Proportion of Variation Explained (PVE).
Results: Of 105 patients with AJCC7 T3 disease, 74 were down-staged. Overall, the prognostic performance of pT7 and pT8 were similar. However, in patient's ≥55 years old without macroscopic ETE or distant metastases, pT8 was inferior to pT7 on the basis of higher AIC, lower C-index (0.67 versus 0.76) and lower PVE (30% versus 45%). In this subset, m-ETE was associated with multiple other adverse prognostic features and reduced DFS (HR 2.8; 95% CI: 1.5-5.2, p=0.002), irrespective of tumor size.
Discussion: In our cohort, pT8 was inferior to pT7 in patient's ≥55 years old without macroscopic ETE or distant metastases, in whom T classification impacts TNM stage. Microscopic ETE was strongly associated with other adverse prognostic factors and reduced DFS in this patient subgroup and may be an effective surrogate for disease biology in PTC, irrespective of whether it is an independent prognostic factor.

PMID: 29672723 [PubMed - as supplied by publisher]

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