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Oral Oncol. 2018 Mar;78:80-86. doi: 10.1016/j.oraloncology.2018.01.021. Epub 2018 Feb 20.

Refining the eighth edition AJCC TNM classification and prognostic groups for papillary thyroid cancer with lateral nodal metastasis.

Author information

1
Division of Endocrinology & Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
2
Statistics and Data Center, Research Institute for Future Medicine, Samsung Medical Center, Seoul, Republic of Korea.
3
Division of Breast and Endocrine Surgery, Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
4
Department of Pathology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
5
Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
6
Division of Endocrinology & Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: taehyukmd.kim@samsung.com.
7
Division of Endocrinology & Metabolism, Department of Medicine, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: thyroid@skku.edu.

Abstract

BACKGROUND:

In the eighth edition, TNM staging system omits location of nodal metastasis as a criterion for staging patients with papillary thyroid cancer (PTC). Accordingly, all of non-metastatic N1b PTC patients are classified as stage I or II solely according to an age-cutoff of 55 years. We hypothesized that incorporating other lymph node (LN) factors into TNM staging system would better predict cancer-specific mortality (CSM) in N1b patients.

METHODS:

We enrolled 745 N1b PTC patients without distant metastasis. Alternative prognostic LN factors and cut-off points were assessed using Cox regression and time-dependent ROC analysis. Alternative prognostic groupings were derived based on minimal hazard differences for CSM among groups stratified by LN risk and age. We assessed accuracy of CSM prediction.

RESULTS:

Lateral LN ratio (LNR) >0.3 and largest LN size >3 cm were prognostic factors for CSM. Stage II patients (eighth edition) with LN risk (lateral LNR >0.3 or largest LN size >3 cm) had a much higher CSM rate (20.9%) than those in the same stage without LN risk (3.2%). Alternative prognostic grouping (Group 1, <55 years without LN risk; Group 2, <55 years with LN risk or ≥55 years without LN risk; and Group 3, ≥55 with LN risk) achieved higher proportions of variance explained (PVEs) for predicting CSM (10.7%) than those of the eighth edition TNM staging system (4.8%).

CONCLUSIONS:

The proposed grouping for N1b patients using LN risk can distinguish patients with poor prognosis from those with good prognosis better than the eighth edition TNM staging system.

KEYWORDS:

Lymph nodes; Mortality; Prognosis; TNM staging; Thyroid cancer

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