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I-131 Radiotherapy

Iodine-131 (I-131) is a radioactive material produced in a nuclear reactor that supplies medical isotopes for nuclear medicine procedures. At high, therapeutic doses the radioisotope can be injected intravenously to effectively penetrate and destroy tumor tissues with localized radiation. Your health care provider will take steps to protect your thyroid gland from being medicated. The radioisotope also gives off gamma particles that can be picked up by a specialized gamma camera in a molecular imaging procedure called scintigraphy. I-131 can be combined with a molecular compound that further personalizes therapy and isolates the radiotherapy to specific cells and their physiological functions.


In I-131 radiotherapy, the radioactive material used is radioactive iodine I-131. The patient swallows the radioactive iodine in either liquid or pill form. The I-131 accumulates in and destroys the thyroid cancer cells.

Advantages of I-131 high-dose radiotherapy

Because I-131 radiotherapy has improved the survival rate of patients with differentiated thyroid cancers that have spread to the neck or other areas, it is now the standard treatment for such cases.

Guidelines for I-131 Radiotherapy Patients

Small amounts of radioiodine can remain in the body for up to three months following treatment. Most of the radioiodine is eliminated from the body during the first week after treatment, primarily through urine. Very small amounts are expelled from the body in saliva, sweat and bowel movements. As a result, patients must observe certain precautions to minimize radiation exposure to others.

First 8 Hours Following Treatment:

  • Drink one glass of water each hour and use the bathroom as soon as possible whe you need to empty your bladder. Men should sit on the toilet to decrease splashing. Use a tissue to wipe up any urine on the toilet bowl and flush. Wash your hands.
  • Maintain a minimum distance of 3 feet from all people. You should drive home alone, but if this is not possible, maintain as much distance as possible from other people in the car. You should not use public transportation.


First Two Days Following Treatment:

  • Sleep alone.
  • Do not share cups, glasses, plates or eating utensils. Wash items promptly after using them.
  • Do not share towels or washcloths.
  • Wash your towels, bed linens, underwear and any clothing stained with urine or sweat separately from other laundry.


First Week Following Treatment:

  • Arrangements should be made for others to care for infants and very young children.
  • Avoid kissing and physical contact and maintain a distance of 3 feet or greater from women who are pregnant and minors under 18 years old.
  • Avoid activities where you may be close to others for more than 5 minutes, for example, movie theaters, sporting events and public transportation.


Special Considerations

Breastfeeding Mothers

You must stop breastfeeding before you can be treated with radioiodine. If possible, you should stop breastfeeding for 6 weeks prior to treatment and you should not resume breastfeeding. You may safely breastfeed babies you have in the future.


Radiodine treatment should not be given during pregnancy. Tell your doctor if you are pregnant or could be pregnant. If you are planning to become pregnant, ask your doctor how long you should wait after treatment. You may be advised to delay pregnancy for at least six to 12 months after I-131 treatment, since the treatment exposes the ovaries to radiation.

Radiation Detection

Radiation detection devices, now present in many locations throughout the country, may be sensitive to the radiation levels present in patients who have recently had I-131 radiotherapy. Ask your doctor for a letter describing your medical treatment. This letter of explanation should include your name, contact information for the testing facility, the name of the procedure and date of treatment and 24-hour contact information.