For patients with low-risk thyroid cancer, ablation when indicated could be achieved with 1.1 GBq radioactive iodine after recombinant human thyroid-stimulating hormone (rhTSH) injections, as this combination reduces whole body irradiation and maintains quality of life, according to findings published in The Lancet Diabetes/Endocrinology.
The ESTIMABL1 (ClinicalTrials.gov Identifier: NCT00435851) randomized phase 3 trial assessed radioactive iodine treatment following complete surgical resection in 752 patients with low-risk thyroid cancer.
A total of 92% of patients had complete thyroid ablation at 6 to 10 months, which the authors defined as rhTSH- stimulated serum thyroglobulin concentration ≤1 ng/mL and normal findings on sonographic imaging. The results showed equivalence between low-activity (1.1 GBq) and high-activity (3.7 GBq) radioactive iodine, as well as between rhTSH injections and thyroid hormone withdrawal.
Patients were randomly assigned to 1 of 4 strategies, with each combining 1 of 2 methods of thyrotropin stimulation (administration of rhTSH or thyroid hormone withdrawal) and 1 of 2 radioactive iodine activities (1.1 GBq or 3.7 GBq). Of the original cohort, 726 patients were included in long-term analysis.
At 5-year follow-up, the majority of patients (n=715, 98%) showed no evidence of disease; 4 demonstrated structural disease, 5 had elevated serum thyroglobulin concentration, and 2 showed indeterminate findings on neck ultrasonography. Of this subgroup, 6 individuals received 1.1 GBq radioactive iodine while 5 received 3.7 GBq.
The authors note that an “increasing concentration of postoperative TSH-stimulated serum thyroglobulin at the time of ablation was prognostic for persistent structural disease at the time of ablation, for incomplete ablation status at 6-10 months, and for disease status at last follow-up.”
Thus, undetectable serum thyroglobulin concentrations prior to ablation “is reassuring and might help to avoid use of radioactive iodine in patients with no other risk factors for persistent disease,” they add.
- Schlumberger M, Leboulleux S, Catargi B, et al. Outcome after ablation in patients with low-risk thyroid cancer (ESTIMABL1): 5-year follow-up results of a randomised, phase 3, equivalence trial [published online May 25, 2018]. Lancet. doi: https://doi.org/10.1016/S2213-8587(18)30113-X
This article originally appeared on Endocrinology Advisor