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Radioactive Iodine Treatment Increases Cancer Risk

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Effective treatments for one medical condition can, unfortunately, increase an individual's risk for another medical condition. One clear-cut example of this is the special risk of former cancer patients later developing a second cancer or another serious medical condition related to their earlier cancer treatment.

Radioactive iodine is a time-honored and effective treatment option for hyperthyroidism, a condition in which the thyroid gland is overactive. The thyroid gland naturally "absorbs" iodine in the body. So if the iodine is made radioactive, the absorbed radioactive iodine delivers radiation directly to the overactive thyroid gland, where it "quiets" the gland and treats the condition. A study found that people who received radioactive iodine to treat hyperthyroidism had an overall 25% increased risk of cancer compared to those who did not. Stomach and breast cancer risk were particularly increased.

The researchers found that women who received radioactive iodine were 53% more likely to develop breast cancer compared to those who did not receive radioactive iodine. The increased cancer risk was seen only after five years from the time of radioactive iodine treatment. Because of this delay in the increased risk, and the fact that radiation takes time to induce cancer, the researchers think that the radiation may be the culprit for the increased cancer risk. It's important to note that while cancer risk was increased in treated patients, the fact is that the vast majority of patients treated with radioactive iodine did NOT develop cancer.

If you are being treated or have been treated with radioactive iodine, the findings of this research do not at all mean that your treatment is, or was, wrong. But you and your doctor should consider the findings of this research in your overall care. In recognizing the possibly increased cancer risk resulting from thyroid treatment, your doctor can plan with you and provide to you the counseling, monitoring, and screening appropriate for that increased risk. This might include a more aggressive approach to breast cancer screening, possibly including mammograms starting at an earlier age, as well as other imaging techniques such as MRI.

This article was made possible by an educational grant from GlaxoSmithKline.

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