Thyroid cancer risk in Belarus among children and adolescents exposed to radioiodine after the Chornobyl accident

Department of Epidemiology and Biostatistics, University of California San Francisco, 3333 California Street, Suite 280, San Francisco, CA 94118, USA.
British Journal of Cancer (Impact Factor: 4.84). 01/2011; 104(1):181-7. DOI: 10.1038/sj.bjc.6605967
Source: PubMed


Previous studies showed an increased risk of thyroid cancer among children and adolescents exposed to radioactive iodines released after the Chornobyl (Chernobyl) accident, but the effects of screening, iodine deficiency, age at exposure and other factors on the dose-response are poorly understood.
We screened 11 970 individuals in Belarus aged 18 years or younger at the time of the accident who had estimated (131)I thyroid doses based on individual thyroid activity measurements and dosimetric data from questionnaires. The excess odds ratio per gray (EOR/Gy) was modelled using linear and linear-exponential functions.
For thyroid doses <5 Gy, the dose-response was linear (n=85; EOR/Gy=2.15, 95% confidence interval: 0.81-5.47), but at higher doses the excess risk fell. The EOR/Gy was significantly increased among those with prior or screening-detected diffuse goiter, and larger for men than women, and for persons exposed before age 5 than those exposed between 5 and 18 years, although not statistically significant. A somewhat higher EOR/Gy was estimated for validated pre-screening cases.
10-15 years after the Chornobyl accident, thyroid cancer risk was significantly increased among individuals exposed to fallout as children or adolescents, but the risk appeared to be lower than in other Chornobyl studies and studies of childhood external irradiation.

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    • "Children's increased sensitivity to thyroidal radiation is one of the most important scientific findings from the Chernobyl nuclear accident. The rates of thyroid cancer were greater than expected in children exposed to radioactive isotopes of iodide [42, 43]. A workshop report [44] found evidence for mild goiter in the regions' children suggesting mild to moderate iodide deficiency. "
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    • "Early responders and fire fighters experienced acute high-dose radiation effects leading to death or serious conditions. The only other direct radiation effect of the accident convincingly demonstrated so far was an elevated incidence of thyroid neoplasms among the residents of Belarus, Ukraine and Russia who were exposed to radioactive iodine as children or adolescents [3] [4] [5] [6]. To assess possible radiation-related health risks, the Estonian cohort study of Chernobyl cleanup workers, the first of its kind, was initiated. "
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