Around 1 in 5 people diagnosed with cancer in the UK take part in a clinical trial.
A trial looking at radioactive iodine treatment for thyroid cancer (HiLo)
This trial was looking at radioactive iodine treatment for two types of thyroid cancer called papillary thyroid cancer and follicular thyroid cancer. These 2 types are also called differentiated thyroid cancer. This trial was supported by Cancer Research UK.
People who have thyroid cancer may have radioactive iodine treatment (also called radioiodine) after their surgery.
Some studies had reported that a lower dose of radioactive iodine works as well as the standard higher dose. But overall, research was not clear about this. One of the aims of this trial was to compare the results of people having low dose or high dose radioactive iodine.
The second aim of this trial was to look at the use of an injection called recombinant human thyroid stimulating hormone (rhTSH). After having surgery to remove thyroid cancer, you need to take thyroid hormone tablets to replace the hormones your thyroid gland would normally make. You usually have to stop taking thyroid hormones for 2 to 4 weeks before having radioactive iodine. During this period people have symptoms of
If you have an injection of rhTSH on each of the 2 days before radioactive iodine treatment, you don’t have to stop taking your thyroid hormones. But doctors were not sure whether rhTSH would affect the way radioactive iodine worked. So this trial compared the results of treatment, with or without rhTSH.
Summary of results
The trial team found that a lower dose of radioactive iodine and rhTSH worked as well as high dose radioactive iodine and caused fewer side effects.
The trial recruited 438 people and the researchers have results for 421 of them. Everybody taking part had stage T1, 2 or 3 thyroid cancer which may have spread to their
The trial was randomised. People taking part were put into 1 of 4 groups by a computer. Neither they nor their doctors could choose which group they were in. After surgery, the different groups had
- Low dose radioactive iodine and rhTSH
- High dose radioactive iodine and rhTSH
- Low dose radioactive iodine without rhTSH
- High dose radioactive iodine without rhTSH
People who didn’t have rhTSH had to stop taking their thyroid hormone tablets before having radioactive iodine treatment.
The researchers found that people who had low dose radioactive iodine spent less time in hospital than people who had the higher dose. More than 1 in 3 people having high dose radioactive iodine (36%) had to stay in hospital for at least 3 days. This figure was just over 1 in 10 (13%) for people who had the lower dose.
To see how successful the treatment was, the trial team looked at the results of scans using gamma camera and blood tests. They found the treatment had been successful in
- 182 out of 214 people who had low dose radioactive iodine
- 184 out of 207 people who had the higher dose
The success rates were also very similar when they compared results for people who had rhTSH and people who did not. They found the treatment was successful in
- 183 out of 210 people who had rhTSH
- 183 out of 211 people who did not have rhTSH
The trial team concluded that low dose radioactive iodine worked as well as the higher dose and that this was not affected by having rhTSH. People having the lower dose of radioactive iodine had fewer side effects, spent less time in hospital and had a better
We have based this summary on information from the team who ran the trial. The information they sent us has been reviewed by independent specialists (
How to join a clinical trial
Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.
Dr Ujjal Mallick
Cancer Research UK
National Institute for Health Research Cancer Research Network (NCRN)
University College London (UCL)
This is Cancer Research UK trial number CRUK/06/030.
If you have questions about the trial please contact our cancer information nurses
Freephone 0808 800 4040