RAI Part 1
This is only used for Papillary and Follicular thyroid cancers.

Like ordinary iodine in the diet, radioactive iodine is taken up by any remaining normal thyroid cells and potentially by thyroid cancer cells as well. The radioactive form of iodine is used to destroy any remaining thyroid cells.

Before this treatment can be given, the patient needs to be prepared so that the treatment stands the best chance of working

Preparing for RAI
Step 1 - Low Iodine Diet

This is recommended in order to get as much of the radioactive iodine to the treatment areas of the body and to stop iodine in the diet from interfering with the treatment.

There is quite a variation in the amount of time that different hospitals and doctors suggest for the low iodine diet.

You are likely to be asked to cut down the amount of iodine in your diet for between 1 and 2 weeks before your treatment. You will be able to eat normally again once the treatment has been finished.

The details of the diet will be given by your own hospital team but the main things that contain iodine that you will need to cut down or avoid are fish and dairy produce. You may find examples of low iodine diets in booklets and on internet sites that are not designed for the UK population's diet so it is best to avoid these as they are unlikely to be suitable.

Step 2 - Producing A High Level of Thyroid Stimulating Hormone (TSH)
There are 2 ways of getting this hormone level high enough in the blood to allow the radioactive iodine to do what it needs to do.

• The first option is to stop thyroid hormone medication and allow the body to make a larger amount of TSH than usual. Many people struggle with this and can develop symptoms including tiredness, loss of appetite, weight gain, dry skin, greasy hair, constipation, mood changes and feeling cold.
• The second option is to give the TSH in an artificial way by injections (recombinant human TSH, rhTSH, ‘Thyrogen’™). The injections are given on the 2 days before the radioactive iodine and are given by injection into the muscle in the buttock. This allows the patient to continue on their thyroid hormones throughout the preparation and treatment process.

Side effects from rhTSH are uncommon and generally mild. Some people feel sick, have a headache or feel weak with aching muscles ( like having flu) after their injections. This is best managed with rest, plenty of fluids and paracetamol. A few people have experienced a rash.

rhTSH may not be available everywhere and it isn't suitable for all patients.