Scientific Protocol for the Study of Thyroid Cancer and Other Thyroid Disease in Belarus Following the Chernobyl Accident
The nuclear power plant accident at Chornobyl released large quantities of Iodine-131 and
other radioisotopes of iodine into the atmosphere, contaminating thousands of square
kilometers and exposing millions of people. For this study, a well-defined subset of
Belarusian children under age 18 years at the time of the accident were identified and
examined by well-trained specialists for thyroid disease every two years for three cycles.
The study is a collaborative effort of researchers in Belarus and the United States.
The cohort includes approximately 12,000 persons who were children in 1986, all of whom had
their thyroids measured for radioactivity during the weeks immediately following the
accident. Under a rigid research protocol these subjects received diagnostic thyroid
examinations, including palpation, ultrasound scanning, thyroid hormone and other laboratory
tests. If indicated, they were referred for a fine-needle aspiration biopsy. Interview
information regarding residential, health, diet and lifestyle history are also collected.
All subjects were followed for thyroid cancer morbidity and mortality. Overall, 163 cancers
were identified. Interviews with mothers of the subjects who were less than 10 years of age
at the time of the accident whose memory of events proved inadequate increased the total
accrual to 13,552.
Based on thyroid radiation measurements made in May-June, 1986, and other information
(reconstruction of deposition patterns and environmental pathways of the radioiodines, and
of the location, dietary characteristics, and lifestyle of each person throughout the
exposure period), each person's radiation dose to the thyroid was estimated.
The aim of the study is to assess the early and late morphologic and functional changes in
the thyroid glands of young persons exposed to radiation from radioactive materials released
as a consequence of the Chornobyl nuclear power plant accident, with emphasis on dose- and
Active screening for thyroid cancers ended in September 2006. The third and final thyroid
screening examinations were completed in September 2006, identifying 163 cases of thyroid
cancer during the examination period. Subject accrual through screening is no longer
ongoing. Thyroid and other cancer case ascertainment is underway by linkage to the
Belarusian Cancer Registry. A paper has been published on the radiation dose response for
prevalent thyroid cancer and analyses of incident cancer cases and other thyroid disease are
Kiyohiko Mabuchi, M.D.
National Cancer Institute (NCI)
United States: Federal Government