Radioactive iodine for thyroid cancer

Could this treatment help me?

It is most often considered for certain papillary or follicular thyroid cancers. These are called differentiated thyroid cancers because the cells retain some features of normal thyroid cells. Not everyone with these cancers needs it. It is generally not a treatment for medullary or anaplastic thyroid cancer. Your team will explain whether the aim is to remove remaining thyroid tissue after surgery, reduce the risk of cancer returning or treat known disease.

The medicine contains iodine-131, a radioactive form of iodine, usually swallowed as a capsule or liquid. It delivers radiation to tissue that takes it up. Preparation helps suitable thyroid cells take up the treatment.

Preparing for treatment

A temporary low-iodine diet

A temporary low-iodine diet reduces ordinary iodine available to the body, helping the target tissue take up radioactive iodine. It is commonly used for around one to two weeks before treatment, with an exact stop date given by your team.

This is not a starvation diet, a low-sugar diet or a lifelong restriction. Keep eating enough. Ask for a practical Indian-food list from the team or dietitian.

In India, much household salt is iodised, meaning iodine has been added. Check the label. The plan may restrict iodised salt, seaweed or kelp products, seafood, certain dairy foods and iodine-containing supplements. Low iodine is not the same as no salt: non-iodised salt may be allowed, subject to your other medical advice. Ask the team about foods you usually eat and any prescribed supplements or medicines before changing them.

Your thyroid medicine plan

Thyroid-stimulating hormone (TSH) encourages suitable thyroid cells to take up iodine. The team may raise TSH using injections of a manufactured form, or by temporarily withdrawing thyroid hormone under supervision.

Withdrawal can cause tiredness and other symptoms of low thyroid hormone. It is not necessary for everyone. Ask which approach is planned, how symptoms will be managed and exactly when any stopped medicine should restart. Never stop thyroxine, your thyroid-hormone medicine, on your own.

What to tell the team

• If you are pregnant, might be pregnant or are breastfeeding. Iodine-131 must not be given during pregnancy or breastfeeding.
• If you have recently had iodine-containing contrast dye for a computed tomography (CT) scan, or take amiodarone (a heart-rhythm medicine), iodine supplements, seaweed products or other medicines that may affect preparation.
• If you have kidney problems, urinary leakage, a urinary catheter (a tube that drains urine) or difficulty caring for yourself.
• If you live with children or a pregnant person, share a bed, or cannot arrange the suggested sleeping or travel plan.
• If anxiety about a single room or temporary separation is worrying you.

Breastfeeding needs to stop well before iodine-131 treatment. The American Thyroid Association advises at least six weeks; your team may require a longer interval. It must not be restarted for the current child after treatment. This does not mean that breastfeeding a future child is ruled out. Get a feeding plan early.

On treatment day

The team checks preparation, blood results and pregnancy testing where appropriate. You swallow the capsule or liquid and follow the prescribed food and drink instructions around it.

Depending on the dose, local rules and your circumstances, care may be outpatient or may involve staying in a single room for a few days. Staff still look after you; they simply organise contact to limit exposure. Ask what you can bring, how meals and communication work, and which belongings may need special handling.

Radiation measurements and the discharge assessment help determine when it is appropriate to go home. A scan after treatment, often on a later day, may show where iodine has collected. The treatment's effect develops over time.

Side effects and when to call

Possible effects include nausea, neck discomfort, taste changes, a dry mouth or tenderness around the salivary glands, which make saliva. Tell the team if these interfere with drinking or eating. They will advise on fluids, mouth care and whether or when sour sweets or lemon products are appropriate; do not assume they should be started immediately.

Fertility (the ability to have children) and uncommon longer-term risks depend partly on dose and repeated treatments and should be discussed before treatment. Seek prompt advice for persistent vomiting, signs that you are not getting enough fluid, or worsening swelling. Severe neck swelling with breathing difficulty needs emergency care.

Going home and follow-up

Your written instructions should give dates for sleeping separately, close contact with children or pregnant people, returning to work, travel, sex and contraception (preventing pregnancy). Avoid pregnancy for the period specified by your team.

Follow the toilet and handwashing advice and precautions for contact with urine or saliva. Ask how to handle laundry or personal-care assistance if needed. Carry a treatment letter for travel, since sensitive radiation detectors may pick up residual radioactivity after routine contact restrictions have ended.

Confirm when to restart thyroid hormone and return to your usual diet. Follow-up may include blood tests to monitor thyroid hormone and look for signs of remaining thyroid tissue or cancer, ultrasound and other imaging when needed. Ask which tests you need and who will explain the results.

Questions you may have