RADIATION RISKS OF THYROID CANCER IN CHORNOBYL CLEAN-UP WORKERS USING THE ALTERNATIVE ESTIMATES OF DOSES OF EXTERNAL EXPOSURE. / RADIATsIINI RYZYKY RAKU ShchYTOPODIBNOÏ ZALOZY V UChASNYKIV LIKVIDATsIÏ AVARIÏ NA ChAES Z URAKhUVANNIaM AL'TERNATYVNYKh OTsINOK DOZ ZOVNIShN'OGO OPROMINENNIa.

OBJECTIVE: The objective of this study was to estimate the thyroid cancer radiation risks - excess absolute risk(EAR), excess relative risk (ERR) and attributable fraction of risk (AR) in the cohort of 150,813 Ukrainian male clean-up workers during the 1986-2012 period (more than 25 years after the Chornobyl accident). MATERIALS AND METHODS: The cohort under study of 150,813 Ukrainian men who participated emergency and clean-up work in 1986-1990 was formed based on the data of the Ukrainian State Register of persons affected due toChornobyl accident (SRU). The identification of thyroid cancer cases (216) was carried out by linking the SRU data-base with the National Cancer Registry of Ukraine (NCRU) data. Standardised incidence ratios (SIR) were estimatedcomparing thyroid cancer incidence in the cohort with the corresponding national indices. Excess absolute risk(EAR), excess relative risk (ERR) and attributable fraction of risk (AR) were calculated accounting for the alterna-tive dose estimates. The following sources of the average dose values for Ukrainian liquidators were used: officialtotal external dose records according to UNSCEAR 2008 report and results of external red bone marrow dose recon-struction by the RADRUE method for the cohort sample. For the radiation risk evaluation, these estimates were con-versed to the average external thyroid dose. RESULTS: Results of the long term study (1986-2012) of thyroid cancer risks in a cohort of 150813 Chornobyl clean-up workers («liquidators¼) from Ukraine are presented. Two options for the average thyroid dose estimates were usedfor radiation risks evaluation. According to the SRU and NCRU 216 incident thyroid cancers were diagnosed in 1986-2012 within the studied cohort with an overall SIR of 3.35 (95 % confidence interval (CI) 2.51-3.80). The SIR esti-mates were elevated throughout the entire follow-up period. Investigation of a contribution of the external expo-sure (according to the alternative values) showed the elevated dose associated thyroid cancer rates in the studiedcohort. Alternatively estimated EAR/104 PY Gy were of 1.86 (95 % CI 0.47-3.24) and 2.07 (95 % CI 0.53-3.62);ERR/Gy - 2.38 (95 % CI 0.60-4.15) and 2.66 (95 % CI 0.68-4.64) and AR % (Gy) 70.4 % and 72.7 % Gy. CONCLUSIONS: Obtained results prove the dose dependent increase of thyroid cancer incidence among UkrainianChornobyl clean-up workers. These conclusions are consistent with those received for combined cohort of Belarus,Russia and Baltic States liquidators.

Non-thyroid cancer in Northern Ukraine in the post-Chernobyl period: Short report.

The Chernobyl nuclear power plant accident in Ukraine in 1986 led to widespread radioactive releases into the environment - primarily of radioiodines and cesium - heavily affecting the northern portions of the country, with settlement-averaged thyroid doses estimated to range from 10 mGy to more than 10 Gy. The increased risk of thyroid cancer among exposed children and adolescents is well established but the impact of radioactive contamination on the risk of other types of cancer is much less certain. To provide data on a public health issue of major importance, we have analyzed the incidence of non-thyroid cancers during the post-Chernobyl period in a well-defined cohort of 13,203 individuals who were <18 years of age at the time of the accident. The report is based on standardized incidence ratio (SIR) analysis of 43 non-thyroid cancers identified through linkage with the National Cancer Registry of Ukraine for the period 1998 through 2009. We compared the observed and expected number of cases in three cancer groupings: all solid cancers excluding thyroid, leukemia, and lymphoma. Our analyses found no evidence of a statistically significant elevation in cancer risks in this cohort exposed at radiosensitive ages, although the cancer trends, particularly for leukemia (SIR=1.92, 95% confidence interval: 0.69; 4.13), should continue to be monitored.