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Radioactive iodine treatment is a type of internal radiotherapy|. The radioactive substance used for treatment is the same as that used for radioisotope scanning| but given in larger doses.
It’s mainly taken as capsules, but can be taken as a drink or injected into a vein in your arm (intravenously). It’s a way of giving radiotherapy internally, rather than externally| as high-energy rays.
It’s common for an operation| for papillary or follicular thyroid cancer to be followed by treatment with radioactive iodine. The iodine treatment can destroy tiny amounts of normal thyroid tissue and any cancer cells that are sometimes left behind after an operation. The treatment is sometimes known as thyroid remnant ablation.
The treatment uses a radioactive iodine called iodine131. The thyroid cells absorb the iodine and receive a very high dose of radiation, which will help to destroy them and any cancer cells that might still remain.
Radioactive iodine has very little effect on other parts of the body since other cells don’t absorb iodine as much as the thyroid cells. Radioactive iodine treatment can be repeated if further tests show that thyroid cells are still present.
Radioactive iodine treatment is only used to treat papillary or follicular thyroid cancer. However, it isn’t suitable for all people with these types of thyroid cancer and you will be given a test dose to make sure that your thyroid cells absorb the iodine.
If you are taking thyroid hormones (T3 or T4) these are usually stopped for 2-4 weeks before the treatment. Most people find that stopping the hormone replacement therapy makes them feel very tired, but it’s important that you do this or the radioactive iodine treatment won’t work.
To help overcome the potential problems of stopping your hormone replacement therapy, it may be possible to be treated with recombinant human thyroid stimulating hormone (rhTSH). This drug, also known as thyrotropin alfa (Thyrogen®), is given as two injections into a muscle, usually in the buttock.
It allows you to carry on taking your hormone replacement tablets| and avoid the symptoms of thyroid hormone withdrawal.
Before radioactive iodine treatment you may be asked to start eating a low iodine diet, as too much iodine in your body will make the treatment less effective. You’ll be given advice about which foods to avoid, including the following:
You should also try to cut down on the amount of dairy products that you eat, as these also contain some iodine.
This includes foods such as:
Unfortunately, unlike external radiotherapy, this treatment makes you slightly radioactive for about 4-5 days. During this time the radioactivity will be gradually lost from your body in your urine, bowel motions (stools), blood, saliva and sweat. This means that for a few days you’ll need to be looked after in hospital until the radioactivity has reduced to a safe level.
Very rarely, you may have pain| or feel sick (nausea)|, tired| and/or breathless| after having radioactive iodine treatment. If these side effects occur, let your nurse or doctor know, as medicines can be prescribed to help.
A rare, long-term side effect of radioactive treatment is a dry mouth|. This can happen if the radioactive iodine is absorbed by the salivary glands. Let your doctor know if you develop a dry mouth.
Because of the possibility of unnecessary radiation exposure to the hospital staff and your friends and relatives, certain safety measures are taken while the radioactive iodine is still in your body.
The staff looking after you will explain these restrictions to you in detail before you start your treatment. Each hospital has different routines, and it’s worth visiting beforehand to discuss the procedure with the nursing and medical staff.
You may be admitted to the ward the day before your treatment so that the staff can go over the procedure with you. This is a good time to ask questions and it may help to make a list of them beforehand.
These safety measures and visiting restrictions can make you feel very isolated, frightened and depressed at a time when you want people around you. If you have these feelings it’s important to let the staff looking after you know.
People are different in the way they handle their fears; some find it easier to know everything about their treatment, while others prefer to know as little as possible. If you want any explanations, the staff on the ward will be happy to help you.
It often helps to bring your fears or worries into the open by talking to the staff or to family and friends.
You should not become pregnant, or father a child, while being treated for thyroid cancer, and for six months to a year afterwards. If you are pregnant, you can’t be given radioactive iodine treatment. For this reason, you must tell your doctor if you are, or think you might be, pregnant. Your fertility| shouldn’t be affected by radioactive iodine treatment, although there is a very small risk if you need to have repeated treatments. Your doctor or nurse can give you more information and support about this. If you are breastfeeding, you must stop a couple of days before you are treated with radioactive iodine. Although it isn’t safe to start breastfeeding again after your treatment, it will be safe for you to do so after future pregnancies.
For answers, support or just a chat, call the Macmillan Support Line free (Monday to Friday, 9am-8pm)
If you have any questions about cancer, need support or just want someone to talk to, ask Macmillan.