A screening study of thyroid cancer and other thyroid diseases among individuals exposed in utero to lodine-131 from chernobyl fallout

Abstract

Background: Like stable iodine, radioiodines concentrate in the thyroid gland, increasing thyroid cancer risk in exposed children. Data on exposure to the embryonic/fetal thyroid are rare, raising questions about use of iodine 131 (1-131) in pregnant women. We present here estimated risks of thyroid disease from exposure in utero to 1-131 fallout from the Chernobyl nuclear accident.Methods: We conducted a cross-sectional thyroid screening study (palpation, ultrasound, thyroid hormones, and, if indicated, fine needle aspiration) from 2003 to 2006. Participants were 2582 mother-child pairsfrom Ukraine in which the mother had been pregnant at the time of the accident on April 26,1986, or 2 months after the time during which 1-131 fallout was still present (1494 from contaminated areas, 1088 in the comparison group). Individual cumulative in utero thyroid dose estimates were derived from estimated 1-131 activity in the mother's thyroid (mean 72 mGy; range 0-3230 mGy).Results: There were seven cases of thyroid carcinoma and one case of Hurthle cell neoplasm identified as a result of the screening. Whereas the estimated excess odds ratio per gray for thyroid carcinoma was elevated (excess odds ratio per gray 11.66), it was not statistically significant (P = 0.12). No radiation risks were identified for other thyroid diseases.Conclusion: Our results suggest that in utero exposure to radioiodines may have increased the risk of thyroid carcinoma approximately 20 yr after the Chernobyl accident, supporting a conservative approach to medical uses of 1-131 during pregnancy.