Thyroidectomy without radioiodine noninferior for patients with low-risk thyroid cancer
A follow-up strategy without radioiodine appeared noninferior to an ablation strategy with radioiodine among patients with low-risk thyroid cancer undergoing thyroidectomy, according to study results in The New England Journal of Medicine.
Rationale and methods
Postoperative administration of radioiodine is controversial in the treatment setting for patients with low-risk differentiated thyroid cancer undergoing thyroidectomy.
“In patients with pathological tumor-node-metastasis (pTNM) stage I disease, retrospective studies have shown inconsistent results regarding the usefulness of radioiodine administration,” Sophie Leboulleux, MD, PhD, of Gustave Roussy in Villejuif, France, and colleagues wrote.
Researchers conducted a prospective, randomized, phase 3 trial including 730 patients with low-risk differentiated thyroid cancer undergoing thyroidectomy. They randomly assigned patients to either ablation with postoperative administration of radioiodine after recombinant human thyrotropin injections (n = 389; median age, 52.2 years; 82% women) or no postoperative radioiodine (n = 387; median age, 52.6 years; 83.5% women).
Whether no radioiodine therapy was noninferior to radioiodine therapy according to the absence of a composite endpoint — biologic, functional and structural abnormalities at 3 years — served as the primary objective. Prognostic factors for events and molecular characterization served as secondary endpoints.
For the purpose of this study, researchers defined noninferiority as a between-group difference of less than 5 percentage points among those who did not experience events, such as abnormal foci of radioiodine uptake on whole-body scanning that required subsequent treatment among those in the radioiodine group only, abnormal findings on neck ultrasonography, or elevated levels of thyroglobulin or thyroglobulin antibodies.
Key findings
At the 3-year follow-up, 95.6% (95% CI, 93-97.5) of patients in the no-radioiodine group did not experience an event compared with 95.9% (95% CI, 93.3-97.7) of those in the radioiodine group, which corresponded to a difference of 0.3 percentage points (two-sided 90% CI, 2.7 to 2.2).
Eight patients experienced structural or functional abnormalities and 23 patients experienced 25 biologic abnormalities events.
Patients with a postoperative serum thyroglobulin level of less than 1 ng/mL during thyroid hormone treatment experienced events more frequently. No patients reported treatment-associated adverse events, and researchers observed similar molecular alterations among patients with or without an event.
Implications
“We observed that less than 5% of the patients in the two groups had events that included abnormal findings on whole-body scanning or neck ultrasonography or elevated levels of thyroglobulin or thyroglobulin antibodies during the first 3 years of follow-up,” the researchers wrote. “This rate is concordant with the definition of low-risk thyroid cancer, and our trial showed that the risk for events was not higher in the absence of postoperative administration of radioiodine.”
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