WEDNESDAY, May 18, 2005 (HealthDay News) -- People exposed to radioactive iodine 131 in childhood have an increased risk of thyroid cancer, but this risk may be lowered with both iodine deficiency and supplementation, according to a study in the May 18 issue of the Journal of the National Cancer Institute.
The international study included 276 thyroid cancer patients and 1,300 control subjects in Belarus and the Russian Federation, who were younger than 15 years old at the time of the Chernobyl nuclear power plant accident in 1986. That accident resulted in widespread radioactive contamination in parts of Belarus, the Russian Federation and the Ukraine.
For people living in the affected areas, the main radiation dose was to the thyroid and came from exposure to I-131.
The study, led by the International Agency for Research on Cancer, found a strong association between radiation dose to the thyroid received during childhood and thyroid cancer risk. The risk was three times greater in areas that were iodine-deficient than in other areas.
The study also found the use of potassium iodide as a dietary supplement reduced thyroid cancer risk by a factor of three compared with no potassium iodide supplementation.
The findings indicate that both iodine deficiency and iodine supplementation are major and independent modifiers of thyroid cancer risk after childhood exposure to I-131.
"This result has important public health implications in the case of exposure to radioactive iodines in childhood that may occur after radiation accidents or during medical diagnostic and therapeutic procedures. Indeed, stable iodine supplementation in iodine-deficient populations may reduce the subsequent risk of radiation-related thyroid cancer in these situations," the study authors wrote.
More information
The U.S. National Cancer Institute has more about thyroid cancer.
