BACKGROUND
While less common than adults, thyroid cancer can affect children. As with adults, papillary thyroid cancer is the most common thyroid cancer seen in children. In fact, papillary thyroid cancer often presents with more aggressive disease in children as compared to than in adults, including larger cancers and more frequent spread to lymph nodes and to areas outside of the neck. Despite this more advanced presentation, survival rate in children is higher than in adults with similar disease. Thus, treatment guidelines for childhood papillary thyroid cancer differ from those for adults.

However, there is variation even among children. Ionizing radiation, such as seen after the Chernobyl nuclear accident, causes an increase in papillary cancer in children. A previous study looking at children exposed to ionizing radiation after Chernobyl showed that younger age was associated with recurrent spread to the lymph nodes and spread to the lungs in cases of papillary thyroid cancer. Other studies looking at this have been small. This study was done to further look at the relationship between papillary thyroid cancer recurrence vs age in the pediatric population (very few exposed to ionizing radiation) and to compare this to a young adult population.

THE FULL ARTICLE TITLE
Thiesmeyer JW et al 2023 Prepubertal children with papillary thyroid carcinoma present with more invasive disease than adolescents and young adults. Thyroid 33:214–222. PMID: 36355601.

SUMMARY OF THE STUDY
This is a study using the National Cancer Database which captures 68% of childhood cancer. The patient sample included 4860 pediatric patients (274 prepubertal (before puberty) and 4586 adolescent) and 101,159 young adult patients. Data was collected including age, sex, ethnic background, cancer spread to the lymph nodes or outside of the thyroid, cancer stage and survival. The adolescent and young adult group was 82% female, compared to 64% in the prepubertal group. The prepubertal group more commonly identified as Hispanic (21%) vs 15% of adolescent and 12% of young adult groups.

More aggressive papillary thyroid cancer was found in the prepubertal group vs the adolescent group including frequency of cancers greater than 4 cm (26% vs 13.5%), more spread to the lymph nodes (58% vs. 36%), more extension outside of the thyroid (47% vs. 25%), more spread to the lymph nodes in the neck (67% vs. 52%), and more spread outside of the neck (11.3% vs. 2.2%). Overall, prepubertal patients presented with more advanced disease than adolescents and young adults.

Almost all patients in all groups underwent total thyroidectomy: 90% of both pediatric groups and 87% of the young adult group. Dissection to remove lymph nodes in the neck were more frequent in young adults (50%) vs 30% of adolescents and 18% of prepubertal groups. Most pediatric patients received radioactive iodine therapy (63% of prepubertal and 59% of adolescents) as compared with 50% of the young adult group). Survival did not differ among the groups and continued to be excellent in both groups (99% at 5 years).

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study confirms that papillary thyroid cancer is more advanced at diagnosis in younger vs older children. Despite this difference, survival is excellent in all groups. Previous studies have demonstrated that recurrence is more common in younger patients. This can be important for patient care since cancer recurrence is anxiety provoking and may necessitate additional surgery. Overall, this study is reassuring that the prognosis of papillary thyroid cancer in the vast majority of patients, both young and old, continues to be excellent.

— Marjorie Safran, MD

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