Radioiodine after thyroidectomy does not improve outcomes in patients with low-risk thyroid cancer, according to a phase 3 trial published in The New England Journal of Medicine.

Researchers found no significant difference in functional, structural, or biologic abnormalities at 3 years between patients who received radioiodine and those who did not.

In the phase 3 ESTIMABL2 trial ( Identifier: NCT01837745), researchers evaluated whether thyroidectomy without follow-up radioiodine is non-inferior to thyroidectomy with iodine-131 (1.1 GBq) for patients with low-risk differentiated thyroid cancer.

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The trial included 730 evaluable patients — 363 who were randomly assigned to the radioiodine group and 367 who were assigned to the no-radioiodine group. Baseline characteristics were similar between the groups.

The primary endpoint was the absence of an event at 3 years. An event was defined as the presence of abnormal foci of radioiodine uptake on whole-body scanning that required subsequent treatment in the radioiodine group, abnormal findings on neck ultrasonography in either group, or elevated levels of thyroglobulin or thyroglobulin antibodies in either group.

At 3 years, 95.9% of patients in the radioidine group were event-free, as were 95.6% of patients in the no-radioiodine group (difference, -0.3; two-sided 90% CI, -2.7 to 2.2). This met the study’s criteria for non-inferiority.

Events were reported in 15 patients in the radioiodine group and 16 patients in the no-radioiodine group. There were 8 patients with functional or structural abnormalities and 23 with biologic abnormalities.

Four patients in the radioiodine group and 10 in the no-radioiodine group underwent subsequent treatment, including surgery, radioiodine administration, or both.

Adverse events occurred in 30 patients overall, but none were related to study treatment, according to the researchers. Quality of life scores were similar between the 2 groups, and there were no thyroid-related deaths.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Leboulleux S, Bournaud C, Chougnet CN, et al. Thyroidectomy without radioiodine in patients with low-risk thyroid cancer. N Engl J Med. Published online March 10, 2022. doi:10.1056/NEJMoa2111953

This article originally appeared on Cancer Therapy Advisor