Free 211At has been proposed for therapy of anaplastic thyroid carcinoma (ATC). However, no extensive biodistribution study comparing tumor-bearing and nontumor-bearing mice has previously been performed. The aim of this study was to perform a complete evaluation of the biodistribution of 211At, both for normal and ATC-bearing mice. For comparison, the biodistribution of 125I- was simultaneously studied. Dosimetric evaluations were performed to investigate if (211)At can be used for therapy of ATC.
Methods: Athymic nude mice were subcutaneously injected with either of two human ATC cell lines, HTh83 and KAT-4. Tumor-bearing and nontumor-bearing mice were injected intravenously with 0.3 MBq 211At and 0.3 MBq 125I- simultaneously. The mice were sacrificed 4-24 hours after injection, and the activity concentrations in tissues were determined.
Results: Except for the thyroid, the concentration of 211At was higher than that of 125I- in the tissues. The uptake of 211At was primarily high in NIS-expressing organs. Furthermore, the absorbed doses to these organs were higher than both tumor types.
Conclusions: The biodistribution of 211At and 125I- differed in this animal model. The higher mean absorbed dose from 211At in several organs than in tumor tissue restricts the possibility of using free 211At for therapy of ATC.