Problems of Radiation Medicine and Radiobiology

A. Ye. Prysyazhnyuk¹, N. K. Trotsyuk¹, N. A. Gudzenko¹, V. V. Chumak¹, O. V. Bakhanova¹,
M. M. Fuzik¹, Yu. M. Belyaev¹, Z. P. Fedorenko², Y. L. Gorokh², A. Yu. Romanenko¹,
D. A. Bazyka¹, O. M. Khukhryanska¹

¹State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine», 53 Melnykova str., Kyiv, 04050, Ukraine
²National Cancer Institute, 33/34, Lomonosov str., Kyiv, 03022, Ukraine

RADIATION RISKS OF THYROID CANCER IN CHORNOBYL CLEAN-UP WORKERS USING THE ALTERNATIVE ESTIMATES OF DOSES OF EXTERNAL EXPOSURE

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 to Chornobyl accident (SRU). The identification of thyroid cancer cases (216) was carried out by linking the SRU database with the National Cancer Registry of Ukraine (NCRU) data. Standardised incidence ratios (SIR) were estimated comparing 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 alternative dose estimates. The following sources of the average dose values for Ukrainian liquidators were used: official total external dose records according to UNSCEAR 2008 report and results of external red bone marrow dose reconstruction by the RADRUE method for the cohort sample. For the radiation risk evaluation, these estimates were conversed 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 («liquidators») from Ukraine are presented. Two options for the average thyroid dose estimates were used for 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 estimates were elevated throughout the entire follow-up period. Investigation of a contribution of the external exposure (according to the alternative values) showed the elevated dose associated thyroid cancer rates in the studied cohort. 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 Ukrainian Chornobyl clean-up workers. These conclusions are consistent with those received for combined cohort of Belarus, Russia and Baltic States liquidators.
Key words: thyroid cancer, clean-up workers, Chornobyl accident, radiation doses, radiation risk analysis.

Problems of radiation medicine and radiobiology.
2018;23:200_215. doi: 10.33145/2304-8336-2018-23-200-215.

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