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I-131 Treatment for Thyroid Cancer

For patients with thyroid cancer, I-131, or radioactive iodine, might be recommended if the cancer has spread to the lungs, lymph nodes or another part of the body. It also may be used to destroy any thyroid tissue not removed during surgery.

This treatment is effective because thyroid cells use nearly all of the iodine in the body to produce the thyroid hormone. When I-131 is administered orally by liquid or capsule, the thyroid cells absorb the radioactive iodine. This causes the cancerous thyroid cells, wherever they may be in the body, to stop growing.

In order to be effective, patients must have high levels of TSH, a thyroid stimulating hormone. To achieve a high level of TSH, it may be necessary to not take thyroid hormone pills for a few weeks. The loss of this medication will in turn cause the pituitary gland to release more TSH.

If abstaining from hormone therapy is not recommended by the patient’s physician, an injectable form of TSH called Thyrogen may be given. Patients receive this drug for two days and then have I-131 therapy on the third.

Patients who have I-131 therapy will give off radiation for a period of time. Depending on the strength of the dose, it may be necessary for patients to remain hospitalized for a few days in a special room to protect others from radiation. Other patients may not require any hospitalization. It is important after leaving the hospital that all I-131 patients follow strict instructions in order to protect others from radiation and to do so for the prescribed period of time.

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