Thyroid Cancer I-131 Treatment

Sodium Iodine I-131 is a radioactive material that is used to treat some diseases of the thyroid. It works by putting a high dose of radiation directly into the thyroid gland, without causing much radiation exposure to the rest of the body. It is used in thyroid cancer to destroy any thyroid tissue that might be left in the neck after surgery, or to treat metastases in the neck, the lungs, or the bones

In order for the I-131 to have the maximum effect, the thyroid tissue needs to be clear of outside iodine or thyroid medications. We may ask you to follow a low iodine diet for several days prior to treatment. If you have been on thyroid replacement, your medicine may need to be stopped for 3-6 weeks before we can consider I-131 treatment. You must also wait 6 weeks for treatment if you have had an IVP or a CT scan where you received a contrast [dye] injection. This contrast contains iodine.

The majority of people are never admitted to the hospital for I-131 treatment. However, if your doctor recommends that you need to be admitted to the hospital, you will remain in isolation for 24-72 hours. After getting the I-131, we will ask you to follow these precautions. This helps minimize any unnecessary radiation exposure to your family, friends, or co-workers.

  1. Flush the toilet two or three times each time you urinate for 24 hours after getting the capsule, because your urine also contains a small amount of I-131. Drink lots of fluids, starting 4-6 hours after the treatment, to help flush excess I-131 out of your system.
  2. Do not share eating utensils, food, gum, tastes of food, licks of ice cream, etc for 2 weeks after the treatment, because your saliva will contain a small amount of radioactive iodine. It is okay to wash your dishes and laundry normally.
  3. After treatment, avoid close contact with pregnant women, infants, or toddlers less than 2 years old. This means arms-length distance for the first 2 weeks, on the lap only for the second 2 weeks, and prolonged contact with the neck only after 4 weeks.
  4. General family or work contacts pose no hazard, but intimate contact or contact with your body fluids [blood, urine, saliva, sweat] should be avoided for at least 2 weeks after the treatment. You are not a hazard to the general public in casual contact.
  5. You must not be pregnant at the time of I-131 treatment. If there is any risk that you might be pregnant, let your doctor know at the time of consultation. Your doctor may suggest you wait for 6 to 12 months before you try to become pregnant.
  6. If you are breast feeding, you must stop prior to I-131 treatment, as breast milk will transfer some of the radiation to the baby.

If ANY of the safety precautions will be difficult for you to follow, please inform your physician BEFORE you agree to the treatment.

The side effects from this treatment are relatively mild, although some patients experience a mild sore throat, difficulty swallowing, and occasionally some temporary swelling of the throat or salivary glands. You may take Tylenol for discomfort, but avoid aspirin, as this could interfere with the iodine uptake into the thyroid. You should take your other regular medicines as prescribed. A very uncommon side effect is thyroid storm, which happens if the body releases a large amount of thyroid hormone from the damaged gland. This is very rare, and you may be given a prescription for a beta-blocker, which reduces the side effects of thyroid storm to almost zero.

Although most patients respond to just one dose of I-131, some patients may require a second treatment at some time if they still have visible uptake on a whole body iodine scan. An adult can be treated safely several times with I-131 if needed, without significant late effects. We will advise you when to start [or resume] your thyroid replacement therapy after treatment.