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Thyroid cancer risk in Belarus after the Chornobyl accident
– Reported, January 26, 2013
Convincing evidence exists of an association between exposure to external radiation and an increased risk of thyroid cancer , but risks from internally deposited radioactive iodines were not well studied until recently. The Chornobyl (Chernobyl) nuclear power plant accident resulted in exposure of populations in Ukraine, Belarus and the Russian Federation to large amounts of radionuclides. Those exposed as children or adolescents received comparatively high radiation doses due to the small size of thyroid gland and high consumption of milk contaminated with radioactive iodines.
Patients with thyroid nodules detected either on palpation or ultrasonogram that measured at least 10mm and all nodules that measured 510mm and were sonographically suspicious for malignancy (hypoechogenic, indistinct border, calcified inclusions, extension through the thyroid capsule or suspicious lymphadenopathy) or with diffusely abnormal thyroid tissue accompanied by unexplained cervical lymphadenopathy were referred to the Minsk and Gomel study centres for further evaluation and ultrasound-guided fine needle aspiration (FNA) biopsy.
Thyroid cancers were included in the analysis if they were surgically removed within 3 years of initial screening. Two study pathologists diagnosed thyroid cancers based on examination of tumour tissue. All diagnoses were confirmed by the Chornobyl Tissue Bank (CTB) or an ad hoc international panel of thyroid pathologists. Pre-screening thyroid cancers were defined as cases diagnosed after the accident and reported by subjects at initial screening. Cancers were validated by review of patients’ medical and pathology records.
In studies of external irradiation of the thyroid gland, younger age at exposure was significantly associated with increased risk and the evidence for gender was suggestive although not uniform across studies.
Iodine deficiency is thought to increase radio iodine uptake by the thyroid gland and to modify thyroid function after radiation exposure
Our findings indicate that in a cohort of children and adolescents from Belarus exposed to the fallout from the Chornobyl accident, thyroid cancer is associated with exposure to radioactive material. Future analyses of incident thyroid cancers identified during additional two screening cycles should shed light on the clinical importance of screening-detected tumors and age at exposure and time trends effects.
CREDITS:
L B Zablotska,* E Ron, A V Rozhko, M Hatch, O N Polyanskaya, A V Brenner, J Lubin,G N Romanov, R J McConnell, P O’Kane, V V Evseenko, V V Drozdovitch, N Luckyanov, V F Minenko, A Bouville, and V B Masyakin
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