CHICAGO -- Radioactive iodine treatment for overactive thyroid glands does not appear to raise people's overall risk of dying of cancer, a study found.
Researchers from the National Institutes of Health and eight other hospitals and research centers followed up on more than 35,500 patients who were treated for hyperthyroidism between 1946 and 1964 at 25 clinics in the United States and one in England.
Sixty-five percent had been treated with iodine-131, a radioactive isotope that destroys cells in the thyroid. The rest had portions of their thyroids removed surgically or had been treated with various drugs.
Some doctors had raised fears that the radioactive iodine treatment might cause cancer.
The statistical analysis, published in Wednesday's issue of the Journal of the American Medical Association, found that the patients who received radioactive iodine had an overall cancer death rate no higher than that of the general population.
Among these patients, the researchers did find a small increase in thyroid cancer deaths during the first five years after treatment. But the researchers said some patients may have had undiagnosed thyroid cancer before they received treatment.
"In absolute terms the excess number of deaths was small, and the underlying thyroid disease appeared to play a role," they wrote. "Overall, it appears to be a safe therapy."
In an accompanying editorial, Dr. David S. Cooper of Johns Hopkins University said radioactive iodine, surgery and thyroid drugs all appear relatively effective and relatively safe, but all present problems as well.
"Current therapies for these conditions have all been in use for more than 50 years and are, in reality, just sledgehammer approaches to the problem," Cooper wrote.