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Risk stratification of pediatric patients with differentiated thyroid cancer: Is total thyroidectomy necessary for patients at any risk? .

BACKGROUND
In the recent American Thyroid Association (ATA) guideline for adult differentiated thyroid carcinoma (DTC) patients, risk stratification is clearly defined and lobectomy is acceptable for low-risk DTC. However, risk stratification for children with DTC in the ATA pediatric guidelines is rather unclear, and total thyroidectomy is recommended for all patients with any risk. The aim of this study was to attempt risk stratification based on our experience and to consider the appropriate extent of thyroidectomy, especially for low-risk DTC in the pediatric population.


PATIENTS AND METHODS
The subjects were 153 patients with DTC ≤ 18 years old, including 58 patients ≤ 15 years old and 136 females, who underwent initial curative surgery in our hospital between 1979 and 2014. Underlying pathology was papillary carcinoma in 130 patients and follicular carcinoma in 23. Risk factors related to disease free survival (DFS) were analyzed and risk stratification was performed.


RESULTS
No patient died of the disease and 34 patients (22.2%) developed recurrences. At initial surgery, 30 patients (19.6%) had lymph node metastases diagnosed before initial surgery (cN1) and 9 (5.9%) had gross extrathyroidal extension (ETE). Significant factors related to DFS on multivariate analysis were cN1, ETE, and number of metastatic lymph nodes (NMLNs) ≥ 10, including microscopic MLNs. According to these factors, subjects were divided into 3 categories: low risk (no risk factors, n=89); intermediate risk (1 risk factor, n=37); and high risk (≥ 2 risk factors, n=27). Ten-year DFS rates in the low-, intermediate-, and high-risk groups were 96%, 83%, and 48%, respectively. Only 12% of low-risk patients underwent total thyroidectomy. Since NMLNs become obvious only after surgery, another analysis after excluding "NMLNs" as a factor showed that cN and ETE were significant factors related to poor DFS. According to these 2 factors, risk stratification was attempted in the same manner. Ten-year DFS rates in the low- (no risk factor, n=117), intermediate- (1 risk factor, n=29), and high-risk (2 risk factors, n=7) groups were 92%, 59%, and 43%, respectively. Only 12% of low-risk patients underwent total thyroidectomy.


CONCLUSION
For low-risk patients, lobectomy may be sufficient as the initial surgical procedure.