Radioactive iodine treatment for thyroid carcinoma

What is radioiodine therapy for thyroid cancer?

Radioiodine is given to patients who have had thyroid cancer and had their thyroid removed. The radioiodine given to you will go to any remaining thyroid cells left in your body that could not be removed during surgery, where it will kill off these cells. It is a painless therapy with no significant risk of serious side effects, but it must be done in a special room at a hospital, as you and your body fluids will be slightly radioactive for a short time after the therapy. There may also be some restrictions to follow about close contact with other people after you leave hospital.

How radioiodine is given

The radioiodine is normally given to you as a capsule that you swallow with a glass of water. If you have difficulties swallowing capsules, please inform us. We can arrange for you to be given the iodine in liquid form.

When radioiodine is given

Radioiodine is normally given within three months after the thyroid surgery. It is possible that more than one treatment is needed. Your doctor will let you know if this is the case when you return for a consultation after the first treatment.

Risks and side effects

Radioiodine is an effective treatment that has been given to many thousands of people over decades. Your doctor has assessed your case and found that the benefits from having this treatment far outweigh the risks from the radiation.

Other people (such as your friends and family, and the hospital staff) do not get any benefit from the radiation which is treating you. We try to reduce the radiation they are exposed to as far as possible.

This is no different from any other prescription medication which you would not share with someone who did not need it. You will be given the treatment in a special room in the hospital.

You may have to follow some restrictions about close contact with other people after you are discharged. The staff treating you will follow precautions to protect themselves. Whilst most patients experience no side effects, it is possible that you may experience some soreness in the throat or dryness in the mouth.

Those who are pregnant, breastfeeding, or planning a family

It is very important that you do not have this treatment if you are pregnant or breastfeeding. Please let your doctor know if there is any chance you might be pregnant before the treatment.

If you are currently breastfeeding, you are advised to stop before you have your treatment. It will not affect your ability to breastfeed in future pregnancies.

You are advised not to become pregnant for six months, or father a child for four months after the treatment. If you are planning a family, you may wish to discuss this with your doctor.

There is no evidence that having this treatment will affect your ability to have children in future.

The length of time radioiodine stays in your body

This is different for each patient. Radioiodine that is not taken up in the remaining thyroid tissue is excreted in bodily fluids, mainly in urine, over the first few days after the treatment. The radioiodine that remains in the body decays naturally with time.

Before your procedure

If you are taking replacement thyroid hormone you will need to either stop taking this for a time before the treatment or come into the hospital for some injections. If one of these applies to you, you will be notified about it in writing beforehand. You should carry on taking all other medications as normal unless told to change or stop them by a doctor.

A diet rich in iodine may reduce the effectiveness of the treatment. For two weeks before the treatment you should avoid foods that contain high levels of iodine, such as fish and seafood, and reduce the number of foods such as dairy produce and eggs that you eat.

Your stay in hospital

The length of your stay depends on how much radioiodine you are given, and how quickly it leaves your body. We measure amounts of radioiodine in gigabequerels (GBq). People who are given 1.1 GBq will stay for one night. Most people who are given 3.7 or 5.5 GBq stay for two nights but occasionally need to stay for a longer time.

It is not possible to predict before you arrive if your stay will be longer than typical – the physicist will calculate this from the measurements they take of you during your stay.

Bring whatever you are going to need to have with you during your stay, though remember that there is the possibility that anything you bring may become contaminated. The following list may help you plan what to bring:

• Clothes to wear during your stay. These should be washed separately from other clothes once you get home.
• Toiletries e.g., toothbrush, toothpaste, shaving kit, hairbrush.
• Any food or drink you would like.
• Books, magazines, games etc. to keep you entertained while you are in the hospital.
• Something to wear on your feet e.g., socks or slippers.

When you arrive, you will have some blood samples taken and have a blood pressure and temperature check. Female patients between the ages of 12 and 55 will be asked to take a pregnancy test. A doctor may examine you, and you may be asked to sign a consent form for the treatment if you have not already done so.

Visitors

Visitors are allowed. There will be a lead screen in the doorway to your room, which visitors must stay behind. On the first day visitors can only stay for 20 minutes. For second day onwards they may stay for the duration of normal visiting hours. People who are under the age of 18 or pregnant cannot visit.

On the day of your treatment

A nuclear medicine physicist will come to talk to you about the treatment and answer any questions you have about the radiation. Once you are happy to go ahead, they will give you the radioiodine.

During the treatment

Measurements of the radiation are taken that come from your body. This will require you to stand or lie still while the physicist holds a radiation detector at different distances from you.

After your treatment

The physicist will return once a day during your stay to take more readings like this. They will use these to work out how quickly the radiation is leaving your body, and to calculate any restrictions you will need to follow when you have been discharged.

Once you have had the radioiodine, remain inside the room until you are discharged. There is an ensuite toilet and shower, and meals will be brought to you. You can ask the nursing staff if you need anything else.

On the second or third day of your stay you are taken for a scan in the nuclear medicine department. This is carried out by a nuclear medicine technologist. You will lie on a flat surface for about one hour while the scanner takes images. The detector will come close to you but will not touch you. The technologist is not able to discuss the result of the scan with you.

You then go back to your room on the ward. If it’s possible for you to be discharged that day, the physicist will visit to discuss the restrictions they have calculated for you. They will give you a copy of the restrictions on a yellow card to take home. The ward staff are then informed that you are ready to be discharged. Stay in the room until you are ready to leave. If someone comes to pick you up, they should not come into the room.

If you get a lift home, sit in the back of the car on the opposite side from the driver. You may also be able to go by public transport provided it is not longer than an hour. You will normally have a follow up with your doctor six to eight weeks after the treatment, before which you may be asked to go for a blood test.

Understanding the restrictions after your treatment

Below is an example of the card you will be given when you are discharged. In this context “Prolonged contact” means spending more than an hour with someone and “close contact” means being less than one metre (roughly three feet) away from them.

Avoiding prolonged close contact with someone does not mean that you need to avoid them completely, but you will need to reduce the time you spend with people. For example, sleeping separately from other people or sitting on a chair on the other side of a room instead of next to someone on the sofa.

Journeys on public transport

Avoid journeys on public transport that last longer than one hour. If you are planning a long journey in the weeks following your therapy, it may be better to postpone the therapy until after your trip. Contact nuclear medicine for advice about any planned long journeys.

Places of entertainment

Avoid places like the cinema, restaurants, football matches, or other entertainment where you will be close to another person for a long period.

Close contact with others

Avoid prolonged close contact with children and pregnant women. While some quick contact is okay, you should not sit with a child on your knee or have them cuddled up to you for more than a minute or so. If you have children, you may wish to consider arranging for someone to help with their primary care.

Avoid prolonged close contact with adults that you would normally spend a lot of time with, such as family members, friends, and co-workers. You do not need to worry about people you only see occasionally or people you pass in the street or in the shops.

The workplace

Depending on what your job involves, you may need to delay returning to work. For example, if you work with closely with children you will need to stay off work for longer than if you work by yourself in an office. The physicist will ask you about your work and advise you how long you will need to take off.

Family planning

You should not become pregnant for six months or father a child for four months after the treatment. Once these restriction periods are over the level of radioactivity inside you is low enough that you can go back to normal and will not be of any risk to anyone around you.

Despite this, because the detectors in airports and docks are very sensitive, they can still detect that you have had this treatment for some time afterwards. We recommend that you keep the yellow card with your passport and take it with you if you are travelling abroad for three months after the treatment.

Contamination

For the first three days you will also need to take care to avoid the spread of contamination. Since your bodily fluids will be radioactive, it is important to make sure that these do not come into contact with other people.

For the first three days:

• Sit down while using the toilet. Close the lid and flush the toilet twice after use. Wash your hands thoroughly.
• Shower at least daily, and wash your hands often, especially before handling things that other people use. Use a separate towel for the first three days.

Do not share cutlery, or taste from the spoon during cooking. Don’t prepare food for others for the first three days.

Low iodine diet

A diet that is high in iodine could interfere with your radioiodine treatment. If there is already lots of non-radioactive iodine in your body, you will not take up as much of the radioiodine dose. Reducing the amount of iodine that you eat will help to make sure you take up the radioiodine and make sure your treatment is effective.

You do not need to avoid iodine all together – it is not possible or necessary to follow a no iodine diet!

You should start following the low iodine diet two weeks before your treatment. After you have had the radioiodine, you can return to your normal diet. If you accidentally eat something that is high in iodine do not worry. This is unlikely to affect your treatment and can still go ahead as planned.

Be aware that sources of information on the internet often tell you to avoid other foods, like salt, or foods which contain salt. In some countries iodine is added to things like salt. This is not done in the UK, so you do not need to worry.

Food guidance

Eat freely

• Fruit.
• Vegetables.
• Meat.
• Table salt.
• Milk substitutes e.g., rice, coconut, almond or soya milk.
• Rice.
• Pasta.
• Bread.
• Potatoes.
• Water.
• Juice.
• Black tea/coffee.
• Olive oil.
• Non-dairy spread.
• Crisps.

Limit

• Milk (25 ml per day).
• Cheese (25 g per week).
• Butter (5 g per day).
• Egg (one per week).

Avoid

• Fish/seafood, seaweed, kelp, laverbread.
• Sea salt/Himalayan salt/iodised salt.
• Supplements containing iodine.
• Cough mixture.
• Foods that contain eggs/dairy, e.g., cakes, custard, milk/white chocolates, mayonnaise.
• Foods coloured with E127 e.g., glacé cherries.