Radioactive Iodine Therapy
Radioactive iodine therapy has been used to treat thyroid overactivity and thyroid cancer since the 1950’s. Thyroid cells are natural-born iodine sponges that soak up dietary iodine from the blood and convert this iodine into thyroid hormone as part of their normal daily function. Physicians give an oral radioactive form of iodine to act as a guided missle to kill overactive thyroid cells or thyroid cancer cells.
In the case of thyroid cancer, radioactive iodine (RAI) is given orally about 3-4 weeks after the thyroid is removed surgically. In order for the RAI to be maximally effective, the patient needs to have a blood TSH level in excess of 25 (must be off thyroid hormone for at least 2-4 weeks) and should be on an iodine-restricted diet (no seafood or kelp) for 1-2 weeks. In order to protect family members, the patient is admitted to the hospital for 24 to 48 hours of radioactive isolation when the RAI is administered.
In most cancer patients, the dose ranges from 75 to 200 millicuries. Usually, these doses are very well tolerated, but may cause neck discomfort and salivary gland (spit gland) tenderness and swelling in a small minority of patients. On the day of discharge from the hospital, the endocrinologist starts thyroid hormone therapy and schedules a follow-up check of thyroid hormone blood levels in 6-8 weeks. Subsequent to discharge, we instruct patients to avoid intimate contact with other human beings (especially children) for one week.
In summary, radioactive iodine therapy is a very effective means to kill microscopic amounts of thyroid cancer left in the neck after thyroid cancer surgery. At Ft. Lauderdale Endocrine Surgery, we use RAI in most patients whose thyroid cancers exceed 1/2 of an inch in size (greater than 2 cm) or exhibit aggressive characteristics on pathologic evaluation. Optimal thyroid surgery with careful lymph node excision in combination with moderate radioiodine dosing results in thyroid cancer cure in most of our patients.
We are frequently asked if the use of therapeutic radioactive iodine can lead to other cancers later in life. Up until recently, the answer seemed to be a definitive “no.” However, a recent cohort study (not the best study format) out of Scandinavia has suggested a small excess risk for cardiovascular disease and non-thyroidal cancers in RAI treated patients followed for many years. Obviously, this situation concerns us greatly and because of the possibility of a small risk of adverse long term outcomes (over 20-40 years), we only use RAI to treat thyroid disease when the benefits far out-weigh the risks.
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