Evolving Paradigm in Radioactive Iodine Therapy for Differentiated Thyroid Cancer: Historical Perspectives, Current Practices and Future Directions

Abstract

Therapy with radioactive iodine (I-131) following a total thyroidectomy has been a gold standard in the treatment of differentiated thyroid cancer (DTC) for over 80 years. Over the years, its role has shifted from routine use to a more selective, risk-adapted approach, informed by tumor biology, patient risk stratification and evolving clinical guidelines. This review examines the changing landscape of I-131 therapy, tracing its historical foundations, current indications, and future directions shaped by molecular medicine. We discuss the transition from a standardized, one-size-fits-all treatment approach to an individualized, dynamic stratification model that allows for ongoing risk reassessment and tailored treatment strategies. Key updates in clinical practice, such as the 2015 ATA Guidelines, the 2022 ETA Consensus Statement, and joint SNMMI and EANM nuclear medicine recommendations, are critically examined. We also address ongoing controversies in the management of low- and intermediate-risk patients, including the roles of I-131 whole-body scanning, activity selection, and overall treatment approach. Molecular theranostics is ushering in a new era in DTC management, enabling improved patient selection and more precise treatment. Advances in molecular profiling, imaging, and targeted therapies support a personalized treatment approach that aims to optimize therapeutic decisions while minimizing side effects and enhancing long-term safety.

Keywords: indications; molecular theranostics; radioiodine therapy; risk stratification; thyroid cancer.

Figure 1

Post-treatment WBS planar images, anterior and posterior planes; (a) Post-treatment whole-body imaging following I-131 therapy with 1.2 GBq demonstrates radiotracer uptake in the thyroid bed consistent with residual tissue in the left thyroid lobe. Additional foci of increased activity in both lungs corresponds to pulmonary metastases, and one focus in the lumbar spine is consistent with bone metastasis; (b) Post-treatment whole-body imaging following I-131 therapy with 10.7 GBq shows a new focal area of uptake in the left cervical region, consistent with a metastatic lymph node. Diffuse uptake persists in both lungs, suggestive of widespread pulmonary metastases. The previously visualized lumbar spine lesion is no longer evident, indicating interval resolution of that metastatic focus.

Figure 2

(a) Post-treatment WBS planar images, anterior and posterior planes, demonstrate increased uptake in the thyroid bed, consistent with residual postoperative thyroid tissue; (b) Diagnostic I-131 WBS planar images, anterior and posterior planes, performed one year later, show no abnormal uptake in the thyroid bed or elsewhere.