ABCs of Radioactive iodine for thyroid cancer
Read about what radioactive iodine treatment is, when you have it and how to prepare for it.
What radioactive iodine is
Radioactive iodine treatment is a type of internal radiotherapy. The treatment uses a radioactive form of iodine called iodine 131 (I-131). The radioactive iodine circulates throughout your body in your bloodstream. Thyroid cancer cells pick up the iodine wherever they are in your body. The radiation in the iodine then kills the cancer cells.
Radioactive iodine is a targeted treatment. It is mainly taken up by thyroid cells, having little affect on other cells. The treatment is only suitable for some types of thyroid cancer. It is used for:
- follicular thyroid cancer
- papillary thyroid cancer
It can treat the cancer even if it has spread. But if you have one of these types of thyroid cancer, this treatment may not be necessary or suitable for you. You may have a test dose to see if your cancer cells take up iodine, because not all of them do.
When you have it
Radioactive iodine treatment may be given:
- after surgery, to kill any cancer cells that may have been left behind
- to treat thyroid cancer that has spread
- to treat thyroid cancer that has come back after it was first treated
You may only need to have this treatment once. But, if needed, it can be repeated every 3 months until there is no sign of any thyroid cancer on your scans.
Preparing for radioactive iodine treatment
Before you have radioactive iodine treatment, you may have a man made type of thyroid stimulating hormone called recombinant human TSH (rhTSH) for a few weeks. It helps any thyroid cancer cells in the body to take up radioactive iodine. Or, your doctor may ask you to stop taking your thyroid hormone tablets. They call this thyroid withdrawal.
You stop taking the tablets for 4 weeks if you are taking T4 (thyroxine) or 2 weeks if you are taking T3 (liothyronine). This is because the I-131 works best when the levels of another hormone called TSH (thyroid stimulating hormone) are high. The levels of TSH in your blood start to rise as soon as you stop taking thyroid hormone tablets.
In some situations, your doctors may not ask you to take thyroid hormone tablets until after your surgery and radioactive iodine treatment have finished.
Low iodine diet
You will be asked to start eating a low iodine diet 2 weeks before you have radioactive iodine treatment. You need to have a low iodine diet because too much iodine in your body can stop the treatment working so well. You don’t have to cut the following foods out altogether but have as little as you can. These include:
- iodised table salt or sea salt
- cough medicine
- fish and seafood
- vitamin supplements that say they contain iodine
- dairy products contain some iodine, so you need to cut down on eggs, cheese, milk and milk products.
You should also cut out any food coloured pink with the additive E127. So do not eat:
- spam or salami
- tinned strawberries
- glacé cherries
- pink pastries or sweets (look on the labels for E127)