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In patients with low-risk thyroid cancer undergoing thyroidectomy, a strategy omitting radioiodine was noninferior to an ablation strategy using radioiodine when it came to the occurrence of certain events at 3 years, a phase III trial found.

Less than 5% of patients in both groups experienced events that included abnormal findings on whole-body scanning or neck ultrasonography, and elevated levels of thyroglobulin or thyroglobulin antibodies, during the first 3 years of follow-up, reported Sophie Leboulleux, MD, PhD, of Gustave Roussy in Villejuif, France, and colleagues.

The percentage of patients without an event was 95.6% in the no-radioiodine group compared with 95.9% in the radioiodine group, which met the noninferiority cutoff for the non-use of radioiodine, the authors noted in the .

In a , David S. Cooper, MD, of Johns Hopkins University School of Medicine in Baltimore, noted that by conducting a randomized trial of radioiodine therapy, Leboulleux and colleagues accomplished something that once was considered a "near impossibility."

"Now, Leboulleux et al. have addressed this issue, at least in patients at low risk for recurrence," Cooper wrote, adding that will soon provide data that may or may not confirm the results of this study, known as .

Thus, "it is noteworthy that although radioiodine therapy for differentiated thyroid cancer was introduced in the 1940s and 1950s, we will finally have definitive evidence to enable clinicians to maximize its benefits and minimize its risks," he continued.

According to the study authors, while there is a consensus to avoid radioiodine in patients with a unifocal microcarcinoma (≤10 mm in diameter), the use of radioiodine in other patients with low-risk thyroid cancer has been "controversial in the absence of demonstrated benefits."

The study's primary objective was to assess whether no radioiodine therapy was noninferior to radioiodine therapy as indicated by the absence of a composite endpoint that included functional, structural, and biologic abnormalities at 3 years, such as the presence of abnormal foci of radioiodine uptake on whole-body scanning that required subsequent treatment, abnormal findings on neck ultrasonography, or elevated levels of thyroglobulin or thyroglobulin antibodies.

These events occurred in 16 of 367 patients (4.4%) in the no-radioiodine group and in 15 of 363 patients (4.1%) in the radioiodine group. Events consisted of functional or structural abnormalities in eight patients, and biologic abnormalities in 23 patients.

Event rates were higher in patients with a postoperative serum thyroglobulin level higher than 1 ng/mL, "which suggests that elevated postoperative levels should be an indication for closer follow-up," Leboulleux and colleagues wrote. They also found that a tumor size less than 14 mm was predictive of an event and suggested that this "unexpected finding" could be related to tumor multifocality, which was common among patients in the trial.

Four patients in the no-radioiodine group and 10 in the radioiodine group required subsequent treatments, including surgery and/or radioiodine administration.

Adverse events were reported in 30 patients, none of which were determined to be treatment-related. Patients in both groups had similar scores for quality of life, anxiety, distress, and fear of recurrence, as well as similar frequency of salivary or lacrimal dysfunction at all time points (except for lacrimal discomfort, which was more common in the radioiodine group at 2 months after randomization).

The trial included 776 patients (mean age 52 years, 83% women) with low-risk differentiated thyroid cancer undergoing thyroidectomy for tumors measuring 2 cm or less in diameter at 35 centers across France. They were randomized 1:1 to radioiodine therapy at a dose of 1.1 GBq or no radioiodine therapy. Of these patients, 730 were evaluable at 3 years after randomization.

A molecular analysis of 100 tumor samples from 96 patients showed that 50 samples had a BRAF V600E mutation, which was similarly present in patients with and without events.

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