Monday, May 18, 2009

Long Term Risks of I-131 RAI Treatment

In general, RAI (radioactive iodine) is a safe and effective treatment for the thyroid disorders mentioned in the prior blog posts. When RAI is used as treatment for hyperthyroidism, it is difficult to avoid development of hypothyroidism. Hypothyroidism is, therefore, watched for by your medical team and quickly treated with thyroid hormone pills.

Your doctor should discuss with you the risk of a small increase in the risk of developing thyroid cancers after RAI treatment for hyperthyroidism, although this has not been seen in all studies conducted, enough variables have been documented to warrant an informed discussion about the risk versus the individual benefits of RAI treatment for hyperthyroidism.

Although radiation kills cancer cells, it can also damage normal tissues and, over time, transform a small percentage of normal cells into cancer cells. This "second cancer" (if you are a thyroid cancer patient) develops in or near the previously treated radiation field, usually ten years or longer after initial radiation treatment has ended. The most common type of radiation induced cancer is sarcoma.

Importantly, then is that you must always remember that once you have been treated with RAI for any reason at all you need to have regular exams by your physician for the rest of your life. If you change doctors, see a dentist or have any emergency room treatment you must make sure you advise the treating provider that you have received RAI and when.

Doses of RAI used to treat thyroid cancers can cause permanent problems with the salivary glands leading to loss of taste and dry mouth. However, precaustions are taken to try to prevent these issues (i.e. using lemon drops or sour candy regularly for the first 14 days after RAI treatment). Temporary or permanent decreases in blood cell counts can also occur.


RAI, whether I-123 or I-131, should never be used in a patient who is pregnant or nursing. RAI given during pregnancy can damage the fetus (baby) thyroid gland. RAI given to a woman who is nursing can get into the breast milk and therefore expose the baby to radiation. Also, pregnancy should be put off a minimum of 6 months and preferably 12 months after RAI treatment since the ovaries are exposed to radiation during RAI treatment. Women who have not yet reached menopause are asked to fully discuss these precautions about the use of RAI with their doctors. There is no clear evidence that RAI leads to infertility.


Men who receive RAI treatment for thyroid cancer may have decreased sperm counts and temporary infertility for periods of roughly 2 years. A doctor may discuss sperm banking with male patients who are expected to need several doses of RAI for thyroid cancer treatment.


Since I-131 RAI produces radiation, patients must do their best to avoid radiation exposure to others, particularly pregnant women and children under the age of 18, especially infants and small pets. Therefore, there are certain precautions that patients who have been treated with RAI are expected to follow after their treatment. These guidelines comply with the Nuclear Regulatory Commission and will be reviewed with patients by the medical institutions giving treatment on a case by case basis according to the dose used for individual patients.

Importantly, the amount of radiation exposure markedly decreases as the distance from patients increases. Patients who need to travel within six months from the time after receiving I-131 treatment and/or expect to visit federal government buildings are advised to carry a letter of explanation with them from their doctors. This is because radiation detection devices used at airports or in federal buildings may pick up even radiation levels considered safe and non-harmful to others.

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