Ann Surg Treat Res.  2017 Mar;92(3):117-122. 10.4174/astr.2017.92.3.117.

Significance of micrometastases in the calculation of the lymph node ratio for papillary thyroid cancer

• Chang YW
• Kim HS
• Jung SP
• Kim HY
• Lee JB
• Bae JW
• Son GS

• KMID: 2377552
• DOI: http://doi.org/10.4174/astr.2017.92.3.117

Abstract

PURPOSE
The lymph node ratio (LNR) is an important prognostic factor in papillary thyroid carcinoma (PTC), but micrometastases in cervical lymph nodes (LNs) are not of great clinical importance. In this study, we analyzed the accuracy of prediction of the prognosis depending on whether micrometastases were included in the number of metastatic LNs when calculating LNR.
METHODS
The study included 353 PTC patients who underwent total thyroidectomy with neck LN dissection, and calculated LNR by 2 methods according to whether micrometastases were included in the number of metastatic LNs: Method 1 did not and method 2 did include. To compare the predictive values of LNR by the 2 methods, correlation coefficients and receiver operating characteristic (ROC) curves were analyzed.
RESULTS
Positive correlations were found between LNR and preablation stimulated thyroglobulin (sTg) levels in both methods, but the correlation between method 1 LNR and preablation sTg level was significantly stronger than that for method 2 (Fisher z = 1.7, P = 0.045). The areas under these 2 independent ROC curves were analyzed; the prognostic efficacy of method 1 LNR was more accurate than that of method 2 LNR, and the difference was statistically significant (P = 0.0001).
CONCLUSION
Regional recurrence of PTC can be predicted more accurately by not including micrometastases in the number of metastatic LNs when calculating LNR.

Keyword

Papillary thyroid carcinoma; Lymph nodes

MeSH Terms

Humans
Lymph Nodes*
Methods
Neck
Neoplasm Micrometastasis*
Prognosis
Recurrence
ROC Curve
Thyroglobulin
Thyroid Gland*
Thyroid Neoplasms*
Thyroidectomy
Thyroglobulin

Figure

• 

  Fig. 1 Scatterplots illustrating the correlation between method 1 (A) and method 2 lymph node ratio (LNR) (B) and preablation sTg level. Significant positive correlations are found in both the methods (method 1: r = 0.4392, P < 0.0001; method 2: r = 0.3302, P < 0.0001), but the correlation between method 1 LNR and preablation sTg level is stronger (C; Fisher z = 1.7, P = 0.045).

• 

  Fig. 2 Receiver operating characteristic (ROC) curves for method 1 (A) and method 2 lymph node ratio (LNR) (B). ROC curves comparing method 1 and method 2 LNR (C). In this plot, the method 1 LNR significantly increased the area under the ROC when compared to the method 2 LNR.

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