Study finds link between radioactive iodine doses and cancer death

Radioactive iodine has been used since the 1940s to treat hyperthyroidism, an overactive thyroid. This study is an extension of one that has followed patients in the United States and the United Kingdom treated for hyperthyroidism for nearly 70 years.

Researchers sought to determine the association of doses of radioactive iodine absorbed by organs or tissue with overall and site-specific cancer death. This analysis included 18,805 patients treated with radioactive iodine and with no history of cancer at the time of treatment. Researchers report a modest association between greater organ-absorbed doses of radioactive iodine and risk of death from solid cancer (a mass), including breast cancer. The study has limitations, including uncertainties in the organ dose estimates and a limited ability to detect significant associations for some outcomes because of a small number of cancer deaths and relatively small doses of radioactive iodine to organs other than the thyroid. More studies are needed to compare the risks and advantages of all major treatment options for patients with hyperthyroidism.