, suggesting these patients can be spared the previously common treatment.
The study’s take-home message for clinicians should be to “stop systematic radioiodine ablation administration in low-risk thyroid cancer patients,” lead author Sophie Leboulleux, MD, PhD, said in an interview.
The results were first reported at ENDO 2021 and have now been published in the New England Journal of Medicine by Dr. Leboulleux, of the department of nuclear medicine and endocrine oncology, Gustave Roussy Cancer Institute, Villejuif, France, and colleagues.
While American Thyroid Association (ATA) guidelines already indicate that radioiodine ablation is not routinely recommended after thyroidectomy for patients with low-risk thyroid cancer, the guidance is only a “weak recommendation,” supported by “low-quality evidence.”
However, the new findings should give that level of evidence a much-needed boost, said one expert. “I think the main contribution of this paper is to change the evidence level to ‘high quality,’ therefore making the recommendation ‘strong,’ rather than ‘weak,’ ” David S. Cooper, MD, said in an interview.
Dr. Cooper, professor of medicine and radiology at Johns Hopkins University, Baltimore, wrote an editorial that accompanies Dr. Leboulleux’s study.
The ability to safely spare patients the radioiodine ablation step after thyroidectomy has important benefits in terms of cost and convenience, Dr. Cooper stressed.
ESTIMABL2 trial
The new findings are from the prospective, randomized, phase 3 Essai Stimulation Ablation 2 (ESTIMABL2) trial, in which 730 patients at 35 centers in France with low-risk DTC scheduled to undergo thyroidectomy were enrolled between May 2013 and March 2017.
Patients were randomized to receive either postoperative radioiodine ablation (1.1 GBq) after injections of recombinant human thyrotropin (n = 363) or no postoperative radioiodine (n = 367).
Patients were a mean age of 52 years and 83% were women. About 96% had papillary tumors, and pathological tumor node (pTN) stages were mostly pT1b thyroid with a nodal status of N0 or Nx (81.1%). It is these patients in particular in whom retrospective studies of the use of radioiodine ablation have yielded inconsistent results, Dr. Leboulleux and colleagues noted. Hence, their decision to look at this prospectively.
Outcomes were based on the groups’ rates of events, defined as the presence of abnormal foci of radioiodine uptake on whole-body scanning that required treatment (in the radioiodine group only), abnormal findings on neck ultrasonography, or increased levels of thyroglobulin or thyroglobulin antibodies.
After a 3-year follow-up, the rates of having no events in both groups were very high – and nearly identical – at 95.6% among those receiving no radioiodine ablation and 95.9% in the radioiodine group, for a between-group difference of –0.3 percentage points, which met the criteria for noninferiority for the no-radioiodine group.
Likewise, the events that did occur were nearly equally split between the no-radioiodine group (16 events, 4.4%) and the radioiodine group (15 events, 4.1%).
Among patients who had events, subsequent treatments, including surgery, radioiodine administration, or both, were necessary for four patients in the no-radioiodine group and 10 in the radioiodine group, and additional treatments were not necessary for the other patients who experienced events.
There were no differences between those who did and did not experience events in terms of molecular alterations, and 50 of the tumors had BRAF mutations, with no significant differences between groups.
Of the adverse events that occurred in 30 patients, none were determined to be related to treatment, and there were no thyroid-related deaths.
The recurrence rates align with the rates observed overall with low-risk thyroid cancer, the authors noted.
“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,” they reported.
“This rate is concordant with the definition of low-risk thyroid cancer, and our trial showed that the risk of events was not higher in the absence of postoperative administration of radioiodine.”