Radioactive iodine for differentiated thyroid carcinoma

The aim of radioactive iodine (RAI) in differentiated thyroid cancer (DTC) is ablation of thyroid remnant and/or treatment of residual disease. This review compares guidelines recommending the use of RAI (or not) in DTC, with a focus on randomized trials in low-risk DTC. Molecular genotyping offers therapeutic options in advanced RAI-refractory DTC.

The ESTIMABL2 and IoN trials suggest that thyroidectomy (with or without central compartment lymph node dissection) followed by surveillance is sufficient in low-risk DTC, despite key differences in inclusion criteria, recurrence-definition, and monitoring protocols. RAI practice is tailored in many aspects: selection of intermediate-risk DTC for RAI and activity based on individual factors, including early dynamic risk assessment; lesional dosimetry in advanced DTC; restrictions following RAI; and choice of systemic therapy in the RAI-refractory setting.

RAI in DTC is evolving towards a risk-adapted model. Escalating evidence indicates that RAI may be safely withheld in a large proportion of low-risk DTC. Optimal management of intermediate-risk DTC remains controversial, due to heterogeneity in clinical and pathological characteristics and conflicting data over survival advantage. Well designed studies incorporating molecular genotype may be key in identifying those most likely to benefit from RAI and in elucidating mechanisms of RAI-resistance.