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Radioactive iodine therapy

Radioactive iodine therapy is a type of internal radiotherapy treatment for thyroid cancer. It can also help to diagnose and treat some cancers and other conditions. Read about how it works and radiation safety. 

What is radioactive iodine?

Radioactive iodine is a type of iodine that is radioactive – iodine 131. It is also called radio iodine. You have radioactive iodine as a capsule or a drink. 

Before treatment

You might be asked to eat a low iodine diet before you have treatment with radioactive iodine. Your doctor or specialist nurse might also ask you to change your thyroid hormone medicines or other medicines for a while. 

You have a scan before treatment. This is so your doctor has a clear picture of your thyroid. This might be on the day of your treatment or a few days or weeks before. 

How does radioactive iodine work for thyroid cancer?

Radioactive iodine is a effective type of treatment for cancer of the thyroid gland.

Diagram showing the position of the thyroid gland

This is because the radioactive iodine from the drink or capsule is absorbed into your body and picked up by the thyroid cancer cells, even if they have spread to other parts of the body. The radiation then destroys the cancer cells. 

This is known as targeted radiotherapy because the treatment goes straight to the cancer and has very little effect on healthy cells in the body.

MIBG treatment

Radioactive iodine can be attached to a chemical called MIBG – meta-iodo-benzyl-guanidine. MIBG is taken up by some types of cancer, including:

  • a rare childhood tumour called neuroblastoma
  • a cancer that affects the adrenal glands called phaeochromocytoma
  • carcinoid tumours

Radioactive iodine attached to MIBG can be used in scans to diagnose these tumours. It is also used to treat these tumour types.

Radioactivity safety procedures

Radioactive iodine treatment can make you radioactive for a few days after treatment. Any radioactive iodine that is not absorbed by the thyroid cancer cells leaves your body in your sweat and urine.

The staff tell you about the radiation safety procedures you need to follow.

You need to drink plenty of fluids during your treatment. This helps to flush the iodine out of your body.

You'll be checked regularly for the amount of radiation in your body. You can go home as soon as it falls to a safe level for the people around you, usually after about 4 to 7 days. In the meantime you stay in a single room at the hospital. 

You might be given some safety steps to follow for a while when you get home, for example if you are in contact with children or pregnant women. Your radiotherapy doctor (clinical oncologist), physicist or specialist nurse explain these to you before you leave hospital.

Side effects of radioactive iodine

Side effects of radioactive iodine treatment can include: 

  • inflammation of the salivary glands
  • dry mouth and changes to your taste
  • a swollen or tender neck
  • feeling flushed
  • feeling sick (nausea)

There is a chance of developing an under active thyroid. Speak to your doctor about when they will test for this. You usually have a blood test 4 weeks after the treatment. 

Information and help

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