BACKGROUND
The management of thyroid cancer is different for children as compared to adults. For example, children with thyroid cancer are recommended to undergo total thyroidectomy, even for low risk cancers. In adults, some low risk cancers can be managed with lobectomy instead (a surgery where only one lobe of the thyroid is resected). The reason for this more aggressive surgical approach in children had to do with the often more aggressive behavior of the cancer: recurrence and spread of the cancer outside of the thyroid are more common in children. For the purposes of thyroid cancer recommendations, the definition of the pediatric population is any child 18 years or younger. The authors of this study wanted to find out if 18 years is the appropriate cut off age for the pediatric guidelines.

THE FULL ARTICLE TITLE
Sugino K et al 2022. Cutoff age between pediatric and adult thyroid differentiated cancer: Is 18 years old appropriate? Thyroid 32:145–152. PMID: 34549602

SUMMARY OF THE STUDY
The authors studied 288 patients, all less than 21 years old, who were seen at Ito Hospital, Japan from 1979 to 2004. They followed these patients from 1.4-38 years. They looked at the thyroid pathology, type of surgery, thyroglobulin levels over time and radiology (ultrasound) imaging. The authors divided the patients in groups by age: younger than 15, 15 to 18 years, and over 18 years of age. They looked at the rate of the cancer coming back (recurrence, expressed as disease free survival, DFS) and rate of the cancer recurring in organs outside the neck area (expressed as distant metastasis free survival, DMFS).

The majority of patients had papillary thyroid cancer and over 80% were more than 14 years old. Only 29% of patient had a total thyroidectomy, but 83% had lymph node resection. Only 6% of the patients had radioactive iodine treatment. Overall 7% of the patients had distant metastasis (lung affected) at presentation. There were 3 deaths, all from this last group. After 30 years of follow-up, the DFS was 68% (percent of children that did not have evidence of disease) and the DMFS was 86% (percent of children without evidence of distal metastasis)

No significant difference was found in DFS between the two age cutoff groups. However, DMSF was significantly different between the group younger than 15 years old and over 15 years (less distant metastasis or higher DMSF). There was no difference in DMFS between the group 15-18 and over 18 years of age. Children younger than 15 years, presented with a more aggressive cancer.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Although more studies are needed, it appears that children younger than 15 years old had distinct clinical presentation and cancer behavior, including higher rates of distant metastasis. A cut off age of less than 15 rather than less than 19 may be more appropriate for children with DTC in terms of guiding interventions, perhaps less aggressive for children older than 15.

— Susana Ebner MD

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