Thyroid carcinoma is the most common second malignancy for childhood cancer survivors. Radiation exposure is linked to risk. Thyroid nodules in children have a high risk for malignancy, whether spontaneous or after radiation. Due to the extremely limited available paediatric data, we sought to review a series of patients with thyroid carcinoma, seen over 25 years. Forty-six patients were identified. Thirty-nine (84.8 %) had papillary thyroid carcinoma, five (10.9 %) follicular carcinoma and 2 (4.3 %) medullary thyroid carcinoma (MEN2B). Thirty-three (71.7 %) had childhood radiation exposure (17 females) with thyroid malignancy occurring 6-37 years later. The smallest nodule size found on surveillance to have thyroid malignancy was 4 mm. Thyroid cancer in patients 16 years and under was seen in 22 patients (47.8 %). All had total thyroidectomy, with initial central node clearance from 2005. Diagnostic rTSH stimulated I(123) scan was followed by ablative I(131) if any uptake was seen. Sixteen (32.6 %) had metastases. Twenty-four (52.2 %) had I(131), four requiring multiple courses. Forty-two remain alive and well.
Conclusion: Ultrasound screening is required for early diagnosis as small nodule size is not predictive of benign histology or absence of metastases. Central node clearance provides better outcome. Despite metastatic disease at presentation for some, prognosis is favourable.
What is known: • Incidence of thyroid cancer has been increasing and radiation exposure in childhood cancer survivors is clearly linked to risk. • Published guidelines in many places can only provide very low level evidence due to extremely limited available paediatric data. What is New: • Paper provides good evidence to confirm existing views with the largest cohort of thyroid cancer reported to date in the paediatric age group in Australia, and the largest cohort in Australia where there have been specific high risks of radiation exposure. The only other reported larger studies have come from the Children's Oncology Group and Childhood Cancer Survivor Study [24]. • Using diagnostic rTSH stimulated I(123) scan 6 weeks after surgery helps to determine if radioactive iodine ablation is necessary and limits unnecessary bone marrow exposure for young patients in whom future leukaemia is of greater concern.
Keywords: Childhood radiation exposure; Paediatric thyroid carcinoma; Thyroid neoplasms; Thyroid nodules.