BACKGROUND
Thyroid cancer is the 9th most common cancer in the world. Overall, thyroid cancer has an excellent prognosis. Thyroidectomy followed by radioactive iodine therapy used to be recommended as standard treatment in all patients with thyroid cancer. However, radioactive iodine therapy has its own risks and significantly increases health care costs. Further, recent studies have shown that many patients are at very low risk for complications and recurrence and they may not benefit from radioactive iodine therapy. Therefore, the more recent American Thyroid Association (ATA) guidelines have recommended a less aggressive approach with less extensive surgery and a more selective use of radioactive iodine therapy. Currently, radioactive iodine therapy is not routinely recommended after thyroidectomy for low-risk thyroid cancer patients. There is little evidence to suggest that radioactive iodine therapy may improve death related to thyroid cancer, which is very low, and there is conflicting evidence regarding improving the risk of thyroid cancer recurrence in these patients. This is the first study aimed to directly compare radioactive iodine therapy to no radioactive iodine therapy in patients with low-risk thyroid cancer after total thyroidectomy.

THE FULL ARTICLE TITLE
Leboulleux S et al 2022 Thyroidectomy without radioiodine in patients with low-risk thyroid cancer. N Engl J Med 386:923–932. PMID: 35263518.

SUMMARY OF THE STUDY
This study included low risk adult thyroid cancer patients. The low risk criteria are: cancers smaller than 2 cm within the thyroid, no cancer extension outside the thyroid, no spread of the cancer to lymph nodes in the neck and no aggressive-type cancer. The cancers were either single measuring between 1 cm and 2 cm or several small cancers (smaller than 1 cm and the sum of largest diameters of all cancers being smaller than 2 cm).

All patients underwent total thyroidectomy with or without lymph node removal and had a neck ultrasound after surgery showing no abnormalities. Patients were randomly assigned to receive radioactive iodine therapy or not to receive this treatment. The radioactive iodine therapy group received 30 mCI of I-131 with recombinant human TSH stimulation and had a post-treatment whole body iodine scan. All patients were followed with serum thyroglobulin (Tg) and Tg antibody tests and neck ultrasound over the next 3 years. The study evaluated the number of patients in the two groups who had abnormal test results worrisome for thyroid cancer recurrence during the first 3 years of follow-up, including abnormal findings on neck ultrasound or whole-body iodine scanning after the radioactive iodine therapy and elevated levels of Tg or Tg antibodies. This trial was designed to answer the question of whether the percentage of patients with normal follow-up tests in the no therapy group is similar to the radioactive iodine therapy group.

A total of 776 patients were randomly assigned to the two treatment groups at 35 centers in France between May 2013 and March 2017. Of these, 730 patients were evaluated at 3 years (367 in the no therapy group and 363 in the radioactive iodine therapy group). Most study patients had normal follow-up tests without evidence of recurrence (95.6% in the no therapy group and 95.9% in the radioactive iodine therapy group). A similar number of patients had abnormal follow-up tests with only a 0.3% difference between groups (4.4% in the no therapy group and 4.1% in the radioactive iodine therapy group). A total of 14 patients required additional therapy with surgery, radioactive iodine therapy, or both (4 in the therapy group and 10 in the radioactive iodine therapy group). Analysis of the quality of life, anxiety, fear of recurrence and salivary dysfunction reported by the patients showed similar results in the two groups, while the radioactive iodine therapy group reported more dry eyes. The BRAF V600 mutation was present in more than 50% of patients, however, it was not associated with thyroid cancer recurrence.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
In adults with low-risk thyroid cancer, radioactive iodine therapy has similar outcomes to the group that did not receive radioactive iodine therapy. The presence of the BRAF V600 mutation does not appear to increase the recurrence risk and should not influence the decision for radioactive iodine therapy in this group. This study supports treating patients with low risk thyroid cancers without the use of radioactive iodine therapy.

— Alina Gavrila, MD, MMSC

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