What to Know About Radioactive Iodine Therapy for Thyroid Cancer
Radioactive iodine therapy
The thyroid is the only part of the human body that absorbs iodine. After you've had surgery for thyroid cancer, you may have treatment with radioactive iodine (I-131). The goal of this treatment is to target and kill any remaining thyroid cells or thyroid cancer cells anywhere in your body. Radioactive iodine therapy is used to treat the slow growing differentiated thyroid cancers, also called papillary and follicular thyroid cancer. It is not usually used to treat medullary or anaplastic thyroid cancer, which grow more rapidly and spread more aggressively.
Radioactive iodine therapy and pregnancy
Radioactive iodine can destroy the thyroid in a growing fetus. Be sure to tell your doctor if you might be pregnant before you have this treatment. Your doctor may suggest you wait six months to a year after radioactive iodine therapy before you try to get pregnant.
What happens during therapy
Radioactive iodine therapy is most effective if you have high blood levels of TSH, which causes thyroid cells in the body to take up the iodine. After thyroid surgery, you may be given a drug called Thyrogen (thyrotropin) to raise your TSH levels before treatment. TSH levels can also be raised by not taking thyroid hormone after surgery for a few weeks, but this can cause bothersome side effects such as feeling tired and depressed.
During radioactive iodine therapy for thyroid cancer, you take radioactive iodine as a pill or liquid. It travels throughout your entire body and is ingested by any remaining thyroid cells and kills them. You may have thyroid scans after this type of radiation to show whether you have any more cancer.
What to expect after therapy
You need to take a few precautions after this type of treatment. For instance, you must stay away from other people for a few days after taking radioactive iodine. You may need to stay in the hospital during this time. Your doctor may also suggest that you drink lots of fluids. Fluids will help flush the radioactive iodine out of your system. Your doctor also may suggest that you flush the toilet several times after urinating. This helps rid the toilet of radioactive material. Most radiation from I-131 is gone in about one week. Ask your doctor about other precautions you should take after treatment and how long you need to take them. You also need to know that high doses of I-131 kills normal thyroid cells, which make thyroid hormone. After radioactive iodine therapy, you will need to take thyroid hormone pills to replace the natural hormone that your body no longer can make on its own.
Side effects of radioactive iodine
Radioactive iodine therapy does not usually cause immediate side effects. Some patients may have neck pain, nausea, dry eyes, and dry mouth. Rarely, men may become infertile. Many doctors recommend that women who have undergone radioactive iodine therapy should not get pregnant for six months to a year following treatment. This therapy may also carry a small risk of leukemia later in life.