Having radioactive iodine treatment

Radiotherapy to treat thyroid cancer is usually given as radioactive iodine (a radioactive substance given as a drink or capsule). Cancer cells absorb more radioactive iodine than normal cells, and the cancer cells die.

You may have this treatment after your operation or if the cancer comes back.

Before treatment starts:

  • You’ll be asked to eat a low-iodine diet. Your health professional will give you information about this.
  • You may be asked to stop taking thyroid replacement hormones to allow the iodine to work.
  • You may be given another hormone drug which allows you to keep taking your thyroid hormones. This treatment isn’t suitable for everyone.

Iodine is radioactive so you’ll have to stay in hospital, in a single room, for a few days while the radioactivity leaves your body. Safety measures will be in place, including:

  • no contact with pregnant women and people under the age of 18
  • limits on the time people can spend with you.

Your doctor will talk to you about any safety measures you may need to continue at home for a few days.

Radiotherapy

Radiotherapy is the use of high-energy rays, usually x-rays and similar rays, to treat disease. It works by destroying cancer cells in the area that’s treated.

There are different ways of giving radiotherapy to treat thyroid cancer:


Radioactive iodine

Radioactive iodine is a type of radioisotope treatment that targets thyroid cells. Radioisotopes are radioactive substances given by mouth as a drink or capsules, or injected into a vein. Cancer cells absorb the radioisotope more than normal cells do and receive a higher dose of radioactivity. This causes the cancer cells to die.

It is usually given:

  • to destroy any remaining thyroid tissue in the neck after an operation. This is called radioiodine remnant ablation (RRA)
  • to treat any thyroid cancer that it hasn’t been possible to remove with surgery
  • to treat thyroid cancer that has come back after initial treatment.

The radioactive substance used for treatment is called iodine-131. It is given as a capsule or occasionally as a liquid.

Under normal circumstances the thyroid gland takes up iodine from our diet and uses it to make thyroid hormones. When you have radioactive iodine, the thyroid cells absorb the iodine and receive a very high dose of radiation. This destroys the thyroid cells and any cancer cells that may remain after surgery.

Radioactive iodine has very little effect on other parts of the body, as other cells don’t absorb iodine as much as thyroid cells.

If tests show that some thyroid cells remain after treatment or if the cancer comes back again, the treatment can be repeated.

Preparing for radioactive iodine treatment 

Before radioactive iodine treatment you will usually be asked to start eating a low iodine diet. You may be asked to stop taking your thyroid hormones.

Radioactive iodine treatment for thyroid cancer

Geraldine, a Thyroid Cancer Information Nurse, talks about what to expect if you're having radioactive iodine treatment and Dave shares his experience.

About our cancer information videos

Radioactive iodine treatment for thyroid cancer

Geraldine, a Thyroid Cancer Information Nurse, talks about what to expect if you're having radioactive iodine treatment and Dave shares his experience.

About our cancer information videos


Low iodine diet

You’ll usually be asked to have a low iodine diet for about two weeks before your treatment. This is because having too much iodine in your body may make the treatment less effective. An example of a low iodine diet is listed below. It’s important to follow the advice of your hospital team.

Foods to avoid

  • fish and seafood
  • table salt and sea salt (with added iodine). Table salt and sea salt with no added iodine can be used
  • cough medicines
  • foods that contain the pink food colouring E127, such as salami, glacé cherries, tinned strawberries and red sweets
  • vitamin and food supplements that contain iodine
  • egg yolks
  • food from fast-food chains and takeaways
  • long-life bread.

Foods you can eat

  • fresh and frozen fruit and vegetables
  • fresh and frozen meats
  • rice, pasta and potatoes
  • soft drinks and fruit juices
  • beer and wine
  • tea and coffee
  • plain fats and oils (non dairy)
  • olive oil spread
  • fresh and homemade bread.

You should also try to cut down on the amount of dairy products that you eat, as these contain some iodine. This includes milk and milk products such as milk chocolate and cheese.


Thyroid hormones

Radioactive iodine needs a high level of thyroid stimulating hormone (TSH) to be effective.

Thyroid hormone replacement stops you producing TSH. So you may need to stop taking your thyroid hormones (T3 or T4) 2–4 weeks before your treatment. Your doctor or nurse will tell you when to stop taking them.

You will probably feel very tired during this time. But it’s important to stop taking thyroid hormones or the radioactive iodine treatment won’t work.

Recombinant human thyroid-stimulating hormone (rhTSH)

You may be given recombinant human thyroid-stimulating hormone (rhTSH). This is also known as thyrotropin alfa (Thyrogen®). It is a man-made drug, similar to the TSH produced in your body. It allows you to carry on taking your hormone replacement tablets so you avoid the symptoms of thyroid hormone withdrawal. You will be given two injections 24 hours apart, on the two days before your radioactive iodine. The injections will be given into the buttock (intramuscularly). You will usually have the injections as an outpatient.

rhTSH is not suitable for everyone. Your doctor or specialist nurse can tell you if you’re able to have this treatment.

rhTSH has very few side effects. Possible side effects include:

You can’t have radioactive iodine treatment if you are pregnant. It is important to tell your doctor if you are pregnant or think you might be. If you’re breastfeeding, you must stop 6–8 weeks before you have your radioactive iodine treatment. It isn’t safe to start breastfeeding again after your treatment, but it will be safe for you to do so after future pregnancies.


Having your radioactive iodine

You will usually be admitted to the ward on the day of your radioactive iodine treatment. Because the iodine is radioactive, you will be radioactive for a while after your treatment. The radioactivity gradually leaves your body in your urine, bowel motions (stools), blood (if you are a woman and having a period), saliva and sweat. This means you will need to stay in hospital, in a single room for a few days after your treatment. During this time the level of radioactivity will be measured regularly with a monitor (Geiger counter) and certain safety measures and restrictions will be in place. These will include:

  • no contact with people under the age of 18 and pregnant women
  • restrictions on the length of time visitors and staff can spend with you
  • restrictions on what you can bring into hospital with you.

Each hospital has different routines and the staff looking after you will explain these restrictions in detail before you have your treatment. You may find these safety measures and restrictions difficult, particularly if you have young children. Do let the nursing and medical staff know if you have any concerns. It may be possible to visit beforehand to discuss the procedure with them.

You will be given the radioactive iodine as a capsule or occasionally as a drink. Following this you will be asked not to eat and drink for a couple of hours so the iodine can be absorbed. After this you can eat normally and will be encouraged to drink plenty of fluids. You will need to flush the toilet twice each time you use it and to let the nursing staff know if you spill or splash any urine. You will also be encouraged to have a shower each day.

The length of time you need to take these precautions for will depend on the dose of radioactive iodine you have been given. Your doctor, nurse or medical physicist will give you more detailed information.

‘My employers were great and let me phase myself back in to work after my surgery. Then I needed to have the radioactive iodine treatment, which wasn’t too bad.’ Dave

Dave


Going home

When you go home you will need to continue taking certain precautions. These may include:

  • avoiding close contact with people under the age of 18 and pregnant women
  • limiting close and prolonged contact with people
  • avoiding crowded places such as public transport and cinemas.

The length of time you need to take these precautions for will depend on the dose of radioactive iodine you have been given. Your doctor, nurse or medical physicist will give you more detailed information.

Back to Radioactive iodine