Iodine pills curb radiation-induced cancer risk
A study confirms that exposure in childhood to radioactive iodines, mainly iodine-131, increases the risk of thyroid cancer and suggests that both iodine deficiency and iodine supplementation may be important and independent modifiers of this risk.
These results have important public health implications, researchers say. They think, based on their study, that giving iodine pills to iodine-deficient populations may substantially reduce the risk of thyroid cancer from radioactive iodine exposure in childhood that may occur after radiation accidents or during medical diagnostic and therapeutic procedures.
The accident at the Chernobyl nuclear power plant in April 1986 led to widespread radioactive contamination, especially in parts of Belarus, the Russian Federation, and the Ukraine. In the years after the accident, a very large increase in the incidence of thyroid cancer was noted in young people living in these contaminated areas.
However, important questions linger about how iodine deficiency, which was common in most of the affected areas at the time of the Chernobyl accident, altered the risk of thyroid cancer.
To investigate, Dr. Elisabeth Cardis, of the International Agency for Research on Cancer in Lyon, France and associates studied 276 thyroid cancer patients and 1300 matched cancer-free controls living near the Chernobyl nuclear power plant who were 15 years of age or younger at the time of the Chernobyl accident.
The researchers observed a strong relationship between radiation dose to the thyroid received in childhood and thyroid cancer risk.
Importantly, they found that the risk was three times higher in iodine-deficient areas than in other areas.
They also found that potassium iodine supplementation, which was given to children, mainly in Belarus, after the Chernobyl accident, was associated with one-third the risk of radiation-related thyroid cancer compared with no supplementation.
Cardis and colleagues report their findings in the Journal of the National Cancer Institute.
In an editorial, Dr. John D. Boice Jr., of the International Epidemiology Institute in Rockville, Maryland and Vanderbilt University in Nashville, Tennessee says these new findings provide “new and, if confirmed, provocative information on the risk of radiation-induced thyroid cancer and on the modifying role of diets deficient in stable iodine and of administering iodine supplements months after the exposure has occurred.”
SOURCE: Journal of the National Cancer Institute May 18, 2005.
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