Nuclear Medicine
Only thyroid cells take up iodine, so a capsule of radioactive iodine treats the thyroid from inside. For thyroid cancer, the trials of the last decade show that most patients need a lower dose, and some need none.
Iodine-131 has been used for eighty years for two very different purposes. For an overactive thyroid it is a single capsule. No hospital stay is needed, and the gland settles over the following months. After surgery for thyroid cancer it destroys the remaining thyroid tissue and any iodine-avid tumor cells, and here the dose and even the need for treatment have changed. A low dose works as well as the old high dose. Some patients need none. Send us your pathology, thyroid blood tests and scans, and a nuclear medicine physician will tell you whether radioiodine is right for you, at what dose and how to prepare.
85% vs 88.9%
Ablation success, low against high dose
95.6% vs 95.9%
Event-free at three years, no radioiodine against radioiodine, low risk
92%
Ten-year survival once metastases clear on radioiodine
Free
Nuclear medicine review of your file
Free consultation
Who receives radioiodine?
Four groups of patients.
- Graves disease, the commonest cause of an overactive thyroid, as an alternative to long-term tablets or surgery.
- A toxic nodule or toxic multinodular goiter, where one or more nodules make too much hormone.
- Thyroid cancer after surgery, to destroy the remaining normal thyroid tissue, a step called ablation, in intermediate-risk and some low-risk patients.
- Thyroid cancer that has spread to lymph nodes, lungs or bones and still takes up iodine, at higher doses and sometimes repeated.
For an overactive thyroid
1
Assessment
Blood tests, a thyroid ultrasound and in many cases an uptake scan to confirm the cause and calculate the dose. Antithyroid tablets are stopped a few days beforehand, and a pregnancy test is done for women who could be pregnant.
2
The capsule
You swallow a single capsule with water in the nuclear medicine department and can go home or to the hotel the same day. There is nothing to feel.
3
The months after
The thyroid calms over six to twelve weeks. Most patients become underactive within a year and take a daily thyroid hormone tablet, which is the expected result and simple to manage.
Radioiodine, tablets or surgery
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Treatment choices for Graves disease
| |
Radioiodine |
Antithyroid tablets |
Surgery |
| How it works |
Destroys overactive thyroid cells |
Blocks hormone production |
Removes the gland |
| Time to effect |
Six to twelve weeks |
Weeks |
Immediate |
| Lasting result |
High, one capsule in most patients |
Relapse common after stopping |
Definitive |
| Main drawbacks |
Lifelong thyroid tablets, can worsen active eye disease |
Rash, rare liver and blood side effects |
Operation risks to voice nerves and calcium glands |
- Keep a distance of one to two meters from others for a few days, longer from pregnant women and small children.
- Sleep alone and use separate towels and cutlery for the period the team specifies.
- Drink plenty.
- Empty the bladder frequently and flush twice, since most of the iodine that the thyroid does not take up leaves the body in the urine within the first two days.
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Radioiodine after surgery for low-risk thyroid cancer
| Trial |
Patients |
Comparison |
Result |
| ESTIMABL, France, 2012 |
752 |
1.1 GBq against 3.7 GBq, injected TSH against hormone withdrawal |
Ablation complete in 92 percent, equivalent across doses and methods |
| HiLo, United Kingdom, 2012 |
438 |
1.1 GBq against 3.7 GBq, injected TSH against hormone withdrawal |
Success 85.0 against 88.9 percent. Hospital stays of three days or more 13.0 against 36.3 percent |
| ESTIMABL2, France, 2022 |
730 evaluated |
Low-dose radioiodine against none |
Free of events at three years 95.9 against 95.6 percent |
Low-dose radioiodine plus thyrotropin alfa was as effective as high-dose radioiodine, with a lower rate of adverse events.
HiLo trial, New England Journal of Medicine, 2012
Low dose, or none, in low-risk cancer
What ESTIMABL2 changed
For patients with small, low-risk thyroid cancer removed by total thyroidectomy, ESTIMABL2 compared a low dose of radioiodine with follow-up alone. At three years, 95.6 percent of those who had no radioiodine and 95.9 percent of those who did were free of any sign of disease. Events were more common when the thyroglobulin level after surgery was above 1.
Guidelines now leave radioiodine out for many low-risk patients, and use the low dose of 1.1 GBq when ablation is chosen. For intermediate and high-risk disease, radioiodine remains standard, at doses chosen for the extent of the tumor.
For thyroid cancer
Preparing for treatment
Thyroid cells take up iodine only when stimulated by TSH, the pituitary hormone that drives the thyroid. There are two ways to raise it. Stopping thyroid hormone tablets for four weeks makes the patient temporarily hypothyroid, tired and slowed. Two injections of recombinant TSH on the two days before treatment avoid that, and both trials found the injections as effective for ablation.
A low-iodine diet for one to two weeks beforehand leaves the cells hungry for iodine, which means avoiding iodized salt, seafood, seaweed, dairy in large amounts and supplements containing iodine. CT contrast containing iodine must be avoided for six to eight weeks before, since it floods the cells.
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Metastatic thyroid cancer treated with radioiodine, 444 patients
| Group |
Ten-year survival |
| Metastases cleared on imaging |
92 percent |
| Metastases persisted |
19 percent |
When the cancer has spread
What radioiodine achieves in metastatic disease
A French series of 444 patients with lung or bone metastases from papillary or follicular thyroid cancer, treated over four decades, showed how much depends on the tumor. Two thirds of the patients had metastases that took up iodine, and in 43 percent of those, repeated treatments cleared every sign on the scans. Most cleared after cumulative doses of up to 22 GBq, and nearly half needed more than five years of treatment.
Once the scans were clear, only 7 percent relapsed. Youth helped. So did well-differentiated tumors and small lung metastases, the pattern in which radioiodine reaches every deposit, while for metastases that stop taking up iodine, targeted drugs replace further radioiodine.
Iodine-131 treatment is highly effective in younger patients with iodine-131 uptake and with small metastases.
Long-term outcome of 444 patients, Journal of Clinical Endocrinology and Metabolism, 2006
1
Days one and two
TSH injections and a blood test for thyroglobulin, the marker thyroid tissue releases. The low-iodine diet continues.
2
Day three
The capsule, in a shielded single room on the nuclear medicine ward. You stay one to three days, until the radiation measured at a distance falls below the discharge limit. Visitors are not allowed during this time.
3
Days five to seven
A whole-body scan shows where the iodine went. The report, with the thyroglobulin result, guides follow-up, and thyroid hormone tablets restart the day after the capsule.
A follow-up strategy that did not involve the use of radioiodine was noninferior to an ablation strategy with radioiodine regarding the occurrence of functional, structural, and biologic events at 3 years.
ESTIMABL2 trial, New England Journal of Medicine, 2022
Pregnancy and breastfeeding
Radioiodine is never given in pregnancy, and a pregnancy test is required beforehand. Breastfeeding must stop completely before treatment, and pregnancy should be avoided for six months afterward.
Side effects
After an overactive thyroid dose, side effects are few. A tender neck for a few days is possible. Graves eye disease may flare, especially in smokers and in people with active eye symptoms, and a short course of steroid tablets is given to prevent it when the risk is high.
After cancer doses, the salivary glands may swell and ache, and taste may change for a few weeks. Many centers advise sour sweets and plenty of water. Dry mouth, and in a small minority blocked tear ducts, can persist after repeated high doses given over several years for metastatic disease. Single standard doses leave fertility intact.
How many days in Istanbul, and what decides the cost?
Start with the records below.
- The pathology report of the thyroid surgery, if any, and the operation note.
- Recent thyroid blood tests, including TSH, free T4, thyroglobulin and thyroglobulin antibodies.
- Neck ultrasound and any scans, with a note of any iodine contrast in the past two months.
- For an overactive thyroid, the diagnosis, tablets taken and any eye symptoms.
Purpose decides the stay.
For an overactive thyroid, two to three days cover the assessment and the capsule. For thyroid cancer, plan a week, from the TSH injections to the scan.
Travel home needs care in the first days. Long flights mean hours in close contact with a stranger, so the team times the flight to the radiation readings and gives you a letter for airport detectors, which can register the iodine for several weeks.
Cost depends on the dose, the TSH injections, the shielded room nights and the post-treatment scan. Radioiodine for an overactive thyroid costs far less than a cancer treatment, which needs the injections, the room and the scan on top of a larger dose, and the quote should list each so you can compare it with what the same treatment would cost at home, including the weeks off work that hormone withdrawal would otherwise bring. Your own figure follows the free review of your file.
One coordinator handles your visit. The team works in seven languages, with interpreters for the rest. Ten days before travel, an invitation letter naming the hospital and the physician goes out, and the international patients office books the transfer and a hotel for you and a companion, who stays at the hotel while you are in the shielded room. Halal, vegetarian and diabetic meals are available, and the low-iodine menu is prepared by the kitchen. There is a prayer room, and a request for a female doctor is passed to the department and met wherever the rota allows. Back home, the coordinator stays reachable on the same WhatsApp number.
Radioiodine therapy FAQ
What is radioiodine therapy?
A treatment with iodine-131, taken as a capsule, that concentrates in thyroid cells and destroys them from inside. It treats an overactive thyroid and thyroid cancer after surgery.
Do I need radioiodine after thyroid cancer surgery?
Not always. For low-risk cancer, the ESTIMABL2 trial found follow-up without radioiodine as safe at three years. Intermediate and high-risk patients still benefit.
Is a low dose as effective as a high dose?
For low-risk cancer, yes. Two trials of 1,190 patients found 1.1 GBq as effective as 3.7 GBq, with fewer side effects and shorter hospital stays.
Will I need to stay in hospital?
Not for an overactive thyroid. For cancer doses, one to three days in a shielded single room until the radiation level allows discharge.
How long must I avoid pregnancy after radioiodine?
Six months. Breastfeeding must stop completely before treatment.
Can my family come with me?
Yes. A companion stays at the hotel during the isolation period, and the international patients office arranges the accommodation.
References
- Schlumberger M, Catargi B, Borget I, et al. Strategies of radioiodine ablation in patients with low-risk thyroid cancer. New England Journal of Medicine. 2012;366(18):1663-1673.
- Mallick U, Harmer C, Yap B, et al. Ablation with low-dose radioiodine and thyrotropin alfa in thyroid cancer. New England Journal of Medicine. 2012;366(18):1674-1685.
- Leboulleux S, Bournaud C, Chougnet CN, et al. Thyroidectomy without Radioiodine in Patients with Low-Risk Thyroid Cancer. New England Journal of Medicine. 2022;386(10):923-932.
- Durante C, Haddy N, Baudin E, et al. Long-term outcome of 444 patients with distant metastases from papillary and follicular thyroid carcinoma: benefits and limits of radioiodine therapy. Journal of Clinical Endocrinology and Metabolism. 2006;91(8):2892-2899.
- Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. Thyroid. 2016;26(10):1343-1421.
