A group of Russian and Japanese scientists has determined that people exposed to radiation during the Chernobyl disaster are unlikely to develop recurring papillary thyroid cancer as a result of subsequent treatment with radioactive iodine.
The team said this finding may have consequences both for people accidentally exposed to radiation and for those who have been medically irradiated as a treatment.
The disaster is still the only event to be rated with the highest level, a seven, on the International Nuclear and Radiological Event Scale, according to the International Atomic Energy Agency.
Researchers matched each participating survivor, all of whom were chosen because they had papillary thyroid cancer, with two patients who had papillary carcinomas unrelated to radiation exposure.
Each Chernobyl survivor had been exposed to between 50 milligrays and 3 grays of radiation. The latter exposure level can be fatal, even with medical care, in up to 50 percent of cases, the Merck Manual estimates.
Among these participants, this radiation was associated with the later development of thyroid cancer. The team conducted this study in order to determine if additional radiation - in the form of radioactive iodine therapy - would cause papillary thyroid cancer to recur among those who had previously been irradiated.
They found that the rate of papillary carcinoma recurrence among Chernobyl survivors was not significantly increased by radioactive iodine exposure.
Those treated according to the Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer were most likely to stay free of papillary thyroid cancer.
In the U.S., nearly 45,000 people are diagnosed with thyroid cancer every year, according to the National Cancer Institute.