From the Research
Most papillary thyroid carcinomas exhibit radioactive iodine (RAI) uptake, which is crucial for their management and treatment with RAI therapy after thyroidectomy. Papillary thyroid carcinomas retain the ability to take up iodine, similar to normal thyroid tissue, though typically at lower levels. This uptake occurs because these cancer cells often maintain expression of the sodium-iodide symporter (NIS), the protein responsible for iodine transport into thyroid cells 1. However, the degree of RAI uptake can vary significantly between tumors, with well-differentiated papillary carcinomas generally showing better uptake than poorly differentiated variants. Some papillary thyroid carcinomas, particularly aggressive variants or those that have dedifferentiated, may lose their ability to concentrate iodine, making them less responsive to RAI therapy.
The variability in RAI uptake among papillary thyroid carcinomas is influenced by several factors, including the expression of the NIS and the presence of specific post-translational modifications, such as those regulated by the ribosomal glycosylphosphatidylinositol transamidase (GPIT) complex 1. Studies have shown that downregulation of certain GPIT subunits, like PIGU, can lead to reduced NIS function and RAI avidity, contributing to resistance to RAI therapy 1.
Post-surgical RAI whole-body scans are essential to determine the presence and extent of residual RAI-avid disease, which helps guide treatment decisions regarding the need for and dosing of therapeutic RAI administration 2, 3. The effectiveness of RAI therapy can be influenced by factors such as the tumor's differentiation status, the presence of lymph node metastases, and the extent of surgical resection 3.
In clinical practice, it is crucial to consider the potential for false-positive RAI uptake in the lungs due to conditions like bronchiectasis, which can mimic pulmonary metastases 4. Therefore, accurate interpretation of RAI scans and correlation with clinical and radiological findings are essential for optimal management of papillary thyroid carcinomas.