Thyroid Cancer Coverage from Every Angle

Low-Risk Thyroid Cancer: Searching for the Optimal Ablative Dose of Radioiodine

By: Sarah Campen, PharmD
Posted: Tuesday, October 6, 2020

After 13 years of follow-up, Hanna Mäenpää, MD, PhD, of Helsinki University Hospital, Finland, and colleagues have reported no difference in disease recurrence between patients treated with 1.1 GBq versus 3.7 GBq of radioiodine (I-131) as ablation therapy after thyroidectomy for low-risk papillary and follicular thyroid cancers. The long-term results of the prospective, phase III study were published in Acta Oncologica.

In the single-center conducted from January 2000 to October 2004, 160 patients with histologically confirmed differentiated thyroid cancer were randomly assigned to receive I-131 at either 1.1 GBq (n = 81) or 3.7 GBq (n = 79). Successful ablation was achieved in 56% and 57% of patients in the 1.1 GBq and 3.7 GBq groups; 44% and 43%, respectively, required one or more extra administrations to complete the ablation.

In the 1.1-GBq group, 8.9% of patients with successful initial ablation and 14% of patients who required more than one administration of I-131 eventually relapsed during the 13-year follow-up. In the 3.7-GBq group, 4.4% and 26.5% patients relapsed, respectively. The proportion of patients relapsing did not appear to differ between the groups (P = .591).

The authors explained that long-term follow-up is essential before any conclusions can be drawn because relapses can occur more than 10 years after treatment. “The interpretation of this study represents a step toward clinically significant implications for truly developing practices,” they concluded.

Disclosure: For full disclosures of the study authors, visit


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