We studied thyroid cancer incidence in a cohort of 150,813 male Chornobyl clean-up workers (“liquidators”) from Ukraine by calculating standardized incidence ratio (SIR) using national cancer statistics. Follow-up began on the liquidator’s registration date with the Chornobyl State Registry of Ukraine (the earliest date was 05. 05. 1986) and continued through December 31, 2010, date of thyroid cancer diagnosis, date of death, or date of last known vital status, whichever came first. There were 196 incident thyroid cancers in the study cohort with an overall SIR of 3.50 [95 % confidence interval (CI) 3.04–4.03]. A significantly elevated SIR estimate of 3.86 (95 % CI 3.26–4.57) was observed for liquidators who had their first clean-up mission in the Chornobyl zone in 1986, when levels of external and internal exposure to radiation were highest; the SIR estimates for later calendar years of first clean-up mission, while significantly elevated, were lower. The SIR estimates were elevated throughout the entire follow-up period but were especially high 10–18 years after the accident: 4.62 (95 % CI 3.47–6.15) and 4.80 (95 % CI 3.78–6.10) for the period 1995–1999 and 2000–2004, respectively. Our findings support the growing evidence of increased thyroid cancer rates among Chornobyl liquidators. Although this could be partially attributed to increased medical surveillance, the observed pattern of SIR increase warrants further investigation of a potential contribution of radiation exposure to the elevated thyroid cancer rates in this large population.
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Adult health study
Excess relative risk
Proportional incidence ratio
Standardized incidence ratio
Chornobyl State Registry of Ukraine
Ukrainian National Cancer Registry
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This research was supported by the Intramural Research Program of the NIH, National Cancer Institute (USA). We acknowledge the contribution of Zoya Fedorenko (Ukrainian National Cancer Register, Ukraine), Nataliya Babkina and Nataliya Trotsiuk (National Research Center for Radiation Medicine, Ukraine) to the study execution. We thank Anatoliy Romanenko, Vadim Chumak, Yuriy Belyayev (National Research Center for Radiation Medicine, Ukraine) and Vladimir Drozdovitch (National Cancer Institute, USA) for helpful discussions of study results.
Conflict of interest
The authors declare that they have no conflict of interest.
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Ostroumova, E., Gudzenko, N., Brenner, A. et al. Thyroid cancer incidence in Chornobyl liquidators in Ukraine: SIR analysis, 1986–2010. Eur J Epidemiol 29, 337–342 (2014). https://doi.org/10.1007/s10654-014-9896-1
- Thyroid cancer
- Clean-up workers