Estimation the Maximum Tolerance Activity of Blood by a Simple Algorithm Method in Pediatric Differentiated Thyroid Cancer Patients Treated With Empirical Radioactive Iodine Dosing Based on Risk Stratification.

After total thyroidectomy for pediatric differentiated thyroid cancer (DTC), the subsequent radioactive iodine (RAI) treatment is a robust therapy, the dosing of which is a major concern. This study was designed to evaluate the "as high as safe administration" (AHASA) principle of RAI treatment in pediatric DTC patients based on the maximum tolerance activity (MTA) of blood to certify dosimetry via a simple algorithm method. Twenty pediatric DTC patients were enrolled and received RAI treatment empirical dosing based on risk stratification after total thyroidectomy. The MTA concentration in the blood was estimated by the modified Hänscheid equation. About 6 (30%) patients had tumors larger than 4 cm, 10 (50%) patients had lateral cervical lymph node metastasis, and 4 (20%) patients had recurrent/persistent thyroid cancer and received more than two RAIs. Five (25%) pediatric patients who had higher serum thyroglobulin antibodies levels at initial diagnosis exhibited aggressive clinical manifestations. Body weight-based doses showed wide variability, and the Dutch recommended dose showed underdosing. In addition, lower body weight was associated with a significantly higher blood absorption dose (R  = 0.3849, p = 0.014). No severe adverse effects were observed in patients who received empirical RAI dosage according to the AHASA principle. The presentation of pediatric DTC can be advanced and aggressive. Empirical RAI dosing based on risk stratification is a simple, safe and effective method. In compliance with the AHASA principle, for prepubertal patients with very low body weight, it is necessary to calculate the blood MTA for RAI dose adjustment.