Thyroidectomy without radioiodine in patients with low-risk thyroid cancer: 5 years of follow-up of the prospective randomised ESTIMABL2 trial

BACKGROUND: I administration at 3 years post-randomisation. Here, we report a pre-specified analysis after 5 years of follow-up. METHODS: I uptake on the post-treatment whole-body-scan requiring subsequent treatment, abnormal neck ultrasonography, elevated thyroglobulin levels, increasing titres or appearance of thyroglobulin antibody (using the same laboratory assay), or a combination of these definitions. Non-inferiority of the proportion of patients without an event in one group compared with the other at 5 years after randomisation was shown if this proportion and its CI did not differ by more than -5%. This study was registered on ClinicalTrials.gov (NCT01837745) and is completed. FINDINGS: Of the 776 patients (n=642 [82·7%] female and n=134 [17·3%] male, median age 52·9 years [IQR 42·6-63·1]) enrolled, 698 were evaluable at 5 years. The proportions of patients without events were 93·2% in the no-radioiodine group and 94·8% in the radioiodine group, for a difference of -1·6% (90% CI -4·5 to 1·4). Events consisted of structural or functional abnormalities (n=11) and biological abnormalities (n=31). INTERPRETATION: I administration in low risk differentiated thyroid cancer was confirmed at 5 years. There is no loss of opportunity in following these patients without postoperative ablation. FUNDING: Programme de Recherche Hospitalier Clinique.