The Role of 123I in the Management of Differentiated Thyroid Cancer: A Comprehensive Narrative Review.

Differentiated thyroid carcinoma (DTC) is the most common malignant endocrine tumor, with a generally favorable prognosis. Imaging, including iodine radioactive isotope scintigraphy (IRIS), is crucial for diagnosis and follow-up. While 131I has long been used for both therapeutic and diagnostic purposes, 123I is reserved for diagnostic imaging due to its shorter half-life and γ emissions. This review highlights the utility of 123I scintigraphy, especially in pre-treatment assessment and dosimetry for DTC. It is particularly valuable before radioiodine (RAI) ablation, providing accurate imaging in patients with iodine-refractory (IR) or biochemically incomplete response (BIR) DTC. When compared to post-therapeutic 131I scans, 123I scintigraphy appears to have a lower sensitivity for detecting metastatic lesions, particularly in lymph nodes and lungs. However, its diagnostic performance compared to low-dose diagnostic 131I is more variable, with some studies suggesting superiority due to the absence of stunning. Further research is needed to standardize its use and optimize its role in guiding DTC management.