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Radioactive Iodine Therapy
Radioactive iodine (RAI) therapy has been used to treat overactive thyroids and thyroid cancer since the 1950s. Thyroid cells are natural iodine sponges that soak up dietary iodine from the blood and convert it into thyroid hormone as part of their normal function. Physicians administer an oral radioactive form of iodine to act like a guided missile to kill overactive thyroid cells or thyroid cancer cells.
Administering Radioactive Iodine
In the case of thyroid cancer, RAI is given orally about three to four weeks after the thyroid is surgically removed. In order for the RAI to be maximally effective, the patient needs to have a blood TSH (thyroid-stimulation hormone) level in excess of 25 (must be off thyroid hormone for at least two to four weeks) and should be on an iodine-restricted diet (no seafood or kelp) for one to two weeks. In order to help 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 tenderness and swelling in a small minority of patients. On the day of hospital discharge, the endocrinologist starts thyroid hormone therapy and schedules a follow-up check of thyroid hormone blood levels in six to eight weeks. Subsequent to discharge, patients are instructed to avoid intimate contact with other human beings (especially children) for one week.
Combination of Treatments
In summary, RAI therapy is a very effective means to kill microscopic amounts of thyroid cancer left in the neck after thyroid cancer surgery. At Memorial Center for Integrative Endocrine Surgery, RAI is used in most patients whose thyroid cancers exceed a half inch in diameter (larger than 2 centimeters) or exhibit aggressive characteristics on pathologic evaluation. Moderate RAI dosing combined with optimal thyroid surgery with careful lymph node excision has resulted in a thyroid cancer cure for most patients of R. Mack Harrell, MD, and David Bimston, MD.
Many people ask if the use of therapeutic radioactive iodine can lead to other cancers later in life. Until recently, the answer seemed to be a definitive "no." However, a recent cohort study in Scandinavia has suggested a small excess risk for cardiovascular disease and non-thyroidal cancers in RAI-treated patients who were followed for many years. This situation concerns the center's physicians greatly and because of the possibility of a small risk of adverse long-term outcomes, they use RAI to treat thyroid disease only when the benefits far outweigh the risks.
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