Age cutoff of 14 years may be more suitable than 18 years for pediatric thyroid cancer
A cutoff of age 15 years for pediatric differentiated thyroid cancer care may be more appropriate than the American Thyroid Association’s cutoff of 18 years due to risk factors related to survival rates, according to study data.
In a retrospective review of records from a hospital in Japan, children aged 14 years and younger who underwent surgery for differentiated thyroid cancer were more likely to have lymph node metastasis and gross extrathyroidal extension than teens aged 15 to 18 years, two significant factors affecting disease-free survival and distant metastasis-free survival rates over 10, 20 and 30 years of follow-up.
“When the cut-off age is changed to 15 years, clinical features, such as clinically apparent metastatic lymph nodes and large primary tumor, as well as synchronous distant metastasis, are outstanding characteristics in this age group,” Kiminori Sugino, MD, PhD, vice president and chief surgeon at Ito Hospital in Tokyo, told Healio. “In addition, we also want to emphasize that clinical features were similar between patients aged 15 to 18 years and patients aged 19 to 20 years, and that clinical features of patients aged less than 15 years were strikingly different from those of patients aged 15 to 18 years and patients aged 19 to 20 years.”
Researchers analyzed data from 288 patients aged 20 years and younger who were treated for differentiated thyroid cancer at Ito Hospital between 1979 and 2014. All data were obtained through medical records. Participants were followed for a median of 15.6 years after surgery. Cutoff ages analyzed in the study were age 18 years as recommended in ATA guidelines and age 14 years as used in the pediatric data set in the International Incidence of Childhood Cancer. Distant metastasis-free survival rates were calculated for all participants, and disease-free survival rates were calculated for all patients who underwent initial curative surgery.
Of the study cohort, 2.4% were younger than 10 years, 16% were aged 10 to 14 years, 41% were aged 15 to 18 years and 40.6% were aged 19 to 20 years at diagnosis. Papillary thyroid cancer was found in 250 participants and follicular thyroid cancer in the remaining 38 patients. Total thyroidectomy was performed for 84 patients.
During follow-up, three participants had disease-specific deaths, all of whom had distant metastases at the time of surgery. There were 52 patients who developed disease recurrence during follow-up, of whom 37 had recurrence in the regional lymph nodes, 14 in distant organs and nine in the remnant thyroid.
Disease-free survival rates for the entire study population were 85.3% at 10 years, 76.4% at 20 years and 68% at 30 years, with no differences between age groups. The rates of distant metastases-free survival were 89.3% at 10 years, 87.9% at 20 years and 85.8% at 30 years. Rates in participants younger than 15 years were significantly lower than those aged 15 to 18 years and aged 19 to 20 years (P < .01 for both).
In multivariate analyses, lymph node metastasis, gross extrathyroidal extension and the number of metastatic lymph nodes were significant factors related to disease-free survival. Sex, lymph node metastasis, gross extrathyroidal extension and total thyroidectomy were factors related to distant metastases-free survival. When the cutoff age was set at 15 years, lymph node metastasis and gross extrathyroidal extension were observed more frequently among children under the cutoff age compared with older patients. There was no significant difference between younger and older patients when the cutoff age was set at 18 years.
“The current ATA guidelines state, ‘studies in which 25% to 30% of the cohort are of younger age have shown that young age is associated with persistent disease or recurrence, whereas studies with fewer young children have not confirmed this,’” Sugino said. “Several researchers have already pointed out that young children have aggressive features at presentation, but this was not confirmed statistically due to the rare occurrence of thyroid cancer in young patients. We hope that this study becomes a trigger for further research from other centers about the appropriate cut-off age.”
For more information:
Kiminori Sugino, MD, PhD, can be reached at k-sugino@ito-hospital.jp.
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