Radioactive Iodine Can Be First-Line for Hyperthyroidism, Says UK

Nancy A. Melville

February 04, 2020

New UK guidelines for the treatment of hyperthyroidism, including Graves' disease, place heavier emphasis on the use of radioactive iodine as the frontline treatment for patients unlikely to remain remission-free on the medications, as opposed to the alternative of antithyroid medications as a first choice.

"Our evidence reviews indicated that radioactive iodine is the most clinically and cost-effective treatment for hyperthyroidism," senior author Kristien Boelaert, MD, PhD, who led the guideline committee, told Medscape Medical News.

"Recommending the use of radioactive iodine as first-line treatment for adults with Graves' disease is a change to current practice and should reduce the variation between centers as to when radioactive iodine is considered appropriate," the guidelines further state.

The new recommendations on hyperthyroidism are part of broader guidelines on thyroid disease by the UK National Institute for Health and Care Excellence (NICE), which concludes that radioactive iodine results in cure in as many as 90% of hyperthyroidism cases.

The recommendations were published in a guideline summary in BMJ by research fellow Melina Vasileiou of the National Guideline Centre, Royal College of Physicians, London, UK, and colleagues.

Current guidelines in the UK and Europe typically call for radioactive iodine to be reserved for use as a definitive treatment only after relapse following antithyroid medication treatment. The latest European Thyroid Association guidelines were published in 2018.

Elsewhere guidelines vary, with many, including those by the American Thyroid Association (ATA) — the most recent published in 2016 — generally calling for treatment with either antithyroid medications, radioactive iodine, or total thyroidectomy, in the absence of any contraindications to each treatment option.

"The US tends to use more radioactive iodine, while Europe, Latin America, and Japan lean more toward (perhaps longer) use of antithyroid medications," Angela Leung, MD, an associate clinical professor of medicine in the Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, UCLA David Geffen School of Medicine, told Medscape Medical News.

"Preferences of deciding which treatment option, which may involve more than one option if antithyroid medications are used initially, depend on a variety of factors related to patient desire, comorbidities, and availability of the therapy," she explained.

Concerns including worsening thyroid eye disease, cardiovascular disease, and development of secondary cancers have caused some hesitation in the use of frontline radioiodine therapy.

And one notably controversial article, published last year, suggested a link between radioactive iodine therapy and an increased risk of cancer mortality. However, as reported by Medscape Medical News, the article spurred debate, with the Society for Endocrinology and British Thyroid Association issuing a joint statement urging caution in interpretation of the findings.

Evidence Supporting First-Line Radioactive Iodine

Patients treated with radioactive iodine take a single tablet that contains iodine and a low dose of radiation, which is absorbed by the thyroid. After taking the treatment patients are advised to avoid prolonged close contact with children and pregnant women for a few days or weeks and to avoid getting pregnant or fathering a child for several months. The treatment is likely to lead to an underactive thyroid gland that will require ongoing treatment with thyroid hormone replacement.

In providing evidence in favor of the benefits of radioactive iodine over the risks, the new NICE guidelines cite five randomized controlled trials of people with hyperthyroid disease, which, though defined as "low quality" evidence, collectively indicate that long-term outcomes were improved with radioactive iodine treatment compared with antithyroid drugs — despite the former having a higher risk of thyroid eye disease (also known as Graves' ophthalmopathy).

In addition, eight nonrandomized studies show no evidence of a clinically important increase in cancer diagnoses or deaths between people treated with radioactive iodine or surgery, or between people treated with radioactive iodine and healthy controls, the guideline committee notes.

"The strongest arguments (in favor of radioactive iodine as a first-line therapy) were the likelihood of inducing remission of Graves' disease with radioactive iodine, the finding that radioiodine is a safe treatment (confirmed in the safety review undertaken by NICE), and the reduction in the need for patients to remain on antithyroid drugs, which may have significant side effects and treatment which usually requires repeated hospital visits or follow-up under a hospital service," said Boelaert.

The new guideline does recommend that antithyroid medication is acceptable as the first-line treatment among patients considered likely to achieve remission.

Leung explains that the percentage of patients with Graves' disease who can achieve remission with antithyroid drugs ranges from 30% to 50%. She noted some evidence does suggest the long-term use of the drugs may be acceptable.

"There are some data the relative safety of long-term use of antithyroid drugs (beyond 24 months) for both Graves' disease and autonomous thyroid nodules," Leung elaborated.

Pregnancy Concerns and Cost-Effectiveness of Radioactive Iodine

Radioactive iodine therapy is meanwhile not suitable if malignancy is suspected, if the patient is pregnant or trying to become pregnant, or if the patient has active thyroid eye disease, the experts agree.

Leung noted that although "it is generally advised to not treat Graves' disease with radioiodine if there is concurrent thyroid eye disease, steroids are a proven effective therapy to decrease this risk in select patients."

And among pregnant patients, "antithyroid medications should be minimally used in the lowest possible doses," Leung said, although she added that, despite their potential risks, the drugs "represent a viable option" for this patient population.

"Also, many would actually advocate for total thyroidectomy in women who are thinking of pregnancy in the near future," she noted.

Another factor of relevance in the guideline recommendations — cost — also favors radioactive iodine, the committee notes.

"Economic evidence showed that radioactive iodine was the most cost-effective intervention," they state.

TRAbs Advised for Determination of Hyperthyroidism Cause

The new UK guidelines further underscore the importance of establishing the underlying cause of hyperthyroidism to ensure appropriate treatment, and the preferred method for doing so is the measurement of thyroid-stimulating hormone receptor antibodies (TRAbs).

"It is important to identify the underlying cause of thyrotoxicosis through measurement of TRAbs, or radioisotope scanning, in order to distinguish hyperthyroidism from transient causes of thyrotoxicosis such as transient thyroiditis, which only requires supportive treatment," explained Boelaert, who is consultant endocrinologist and director of the National Institute for Health Research Integrated Academic Training Program at the Institute of Applied Health Research, University of Birmingham, UK.

"In addition, this will help distinguish Graves' disease from toxic nodular hyperthyroidism, which is important as antithyroid drugs are not effective in inducing a cure in the latter," she explained.

Meanwhile, the new guidelines further note that although use of diagnostic ultrasound is informative when palpation suggests thyroid nodules, it is of limited diagnostic value for Graves' disease.

"The recommendation (suggests that) thyroid ultrasonography should only be offered if there is a palpable thyroid nodule," Boelaert noted.

She concluded: "There has been uncertainty in the UK about the best treatment for hyperthyroidism despite radioactive iodine being the most common first-line treatment for this condition in the United States. We are very pleased to have been able to work with NICE to provide clear new guidance which we hope will improve outcomes for patients with this condition."

The National Guideline Centre was commissioned and funded by NICE to develop the guideline. No authors received specific funding to write the summary. Boelaert has reported no relevant financial relationships. Disclosures for the other authors are listed in the article.

BMJ. 2020;368:m41. Abstract

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