CompletedPhase II/IIIInterventional

ION - Is ablative radiOiodine Necessary for low risk differentiated thyroid cancer patients?

Thyroid cancer is commonly treated with surgery to remove the whole thyroid gland. After surgery, many patients also receive radioactive iodine. This treatment uses a capsule of radioactive liquid to destroy any remaining thyroid tissue or cancer cells. However, for patients with low-risk thyroid cancer, doctors are unsure if radioactive iodine is always needed. The ION trial aims to find out if having surgery and daily thyroid hormone tablets is just as safe and effective as having radioactive iodine as well. Participants are split into two groups: one receives radioactive iodine after surgery, and the other does not. Both groups take hormone tablets and have regular check-ups. If the trial shows that radioactive iodine is not needed, future patients could safely avoid hospital stays, dietary rules, and potential side effects from radiation.

At a glance

Status

Completed

Phase

Phase II/III

Sponsor

University College London (UCL) (UK)

Enrolment target

570

Start

16 May 2012

Estimated completion

30 Mar 2020

Differentiated thyroid cancer

What is this study about?

The thyroid is a small gland in the neck that produces hormones to help control your metabolism. When people are diagnosed with differentiated thyroid cancer, the first step is usually surgery to remove the entire gland. Traditionally, many patients are then given a treatment called radioactive iodine ablation. This involves swallowing a radioactive capsule that travels through the body to target and destroy any leftover thyroid cells.

While radioactive iodine has been used for many years, cancers caught early that have not spread are considered 'low risk'. For these low-risk cancers, the chance of the cancer returning is already very small. Doctors want to know whether giving radioactive iodine provides any real extra protection, or if it exposes patients to unnecessary radiation and side effects without added benefit.

In the ION study, researchers are comparing two standard pathways. One group receives radioactive iodine alongside standard daily hormone tablets, while the other group takes the hormone tablets without the radioactive iodine. Both groups are monitored very closely with regular blood tests and neck scans over several years to track their health.

The goal of this study is to help doctors create clearer, kinder treatment guidelines. If the trial shows that patients do just as well without radioactive iodine, future patients with low-risk thyroid cancer can safely skip this treatment, avoiding hospital isolation and side effects while maintaining excellent recovery rates.

Key takeaways

The ION trial tests whether radioactive iodine is truly necessary for low-risk thyroid cancer.
All participants have already had surgery to completely remove their thyroid gland.
Patients are randomly chosen to either receive radioactive iodine or skip it.
Everyone receives daily hormone tablets and close, regular monitoring.
Taking part is completely voluntary and you can stop at any time.

Who may be eligible?

This trial is open to people aged 16 and over who have had surgery to completely remove their thyroid gland for low-risk differentiated thyroid cancer (such as papillary or follicular thyroid cancer). The surgical team must have removed all visible cancer, meaning no known tumour was left behind in the neck.

To take part, your cancer must be contained within or close to the thyroid area, with no signs of having spread to distant parts of the body. You also need to be reasonably well and able to care for yourself day to day. Women who could become pregnant will need a negative pregnancy test before joining.

You cannot take part if your tumour has more aggressive features, such as medullary or anaplastic thyroid cancer, or if it has spread widely to distant organs or many lymph nodes. People whose surgery could not remove all the cancer tissue are also not eligible.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

You are aged 16 or over.
You have had an operation to remove your whole thyroid gland.
Your diagnosis is low-risk papillary or follicular thyroid cancer.
Your surgeon successfully removed all visible tumour.
Your cancer has not spread to distant parts of your body.
You are not currently pregnant.

Answer every question to see your result.

What does participation involve?

If you take part, you will be placed into one of two treatment groups by chance (randomly). One group will receive radioactive iodine, which usually involves a short stay in a specialised hospital room and following a low-iodine diet beforehand. The other group will not receive radioactive iodine. Everyone in the study will take daily thyroid hormone tablets (levothyroxine) to replace the hormones the thyroid used to make. You will attend regular hospital appointments over several years for routine checks, including neck ultrasounds and blood tests to monitor thyroid protein levels. The total study follow-up lasts several years to ensure you remain cancer-free.

Potential risks and benefits

Taking part may mean you can safely avoid radioactive iodine and its possible side effects, such as a dry mouth, temporary changes in taste, and the need to isolate in hospital. If you receive radioactive iodine, you get the standard treatment offered in many hospitals. However, there is a small chance that not having radioactive iodine could slightly alter the risk of the cancer returning, which is why all participants are monitored very closely so any changes can be caught and treated immediately. Joining the study is entirely your choice, and you can withdraw at any time without your regular NHS care being affected.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

Cancer Research UK & UCL Cancer Trials Centre
City only
London, England

Common questions

What is radioactive iodine?

It is a form of radiation given as a capsule or drink. Because thyroid cells naturally absorb iodine, the radiation targets and destroys any remaining thyroid tissue.

How is it decided which group I am in?

A computer puts you into a group at random. Neither you nor your doctor can choose, ensuring the study results are fair and reliable.

Will I still get cancer treatment if I do not get radioactive iodine?

Yes. You will have already had full surgery to remove the tumour, and you will take daily hormone tablets that also help keep cancer cells from returning.

What side effects can radioactive iodine cause?

Short-term side effects can include mild neck swelling, nausea, dry mouth, or changes in taste. You also have to follow safety precautions regarding contact with others for a short time.

Can I leave the study if I change my mind?

Yes, you can withdraw at any point. Your medical team will continue to offer you the best standard care available.

How to find out more

Krystyna Reczko

ion@ctc.ucl.ac.uk +44 (0)20 7679 9878 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.