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Thyroid Cancer Among Young People in Fukushima

Wakeford, Richard; Auvinen, Anssi; Gent, R. Nick; Jacob, Peter; Kesminiene, Ausrele; Laurier, Dominique; Schüz, Joachim; Shore, Roy; Walsh, Linda; Zhang, Wei

Author Information
doi: 10.1097/EDE.0000000000000466
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To the Editor:

Tsuda et al.1 reported the current findings of a large-scale thyroid disease screening program in Fukushima Prefecture, Japan, following the release of radionuclides, in particular iodine-131, from the accident at Fukushima Dai-ichi nuclear power station in March 2011. They suggest that these findings indicate an increase in cases of thyroid cancer that is attributable to the accident. We were members of an International Expert Working Group established by the World Health Organization to perform an initial assessment of the health consequences of the Fukushima Dai-ichi accident,2 and we have serious concerns over this interpretation of Tsuda et al.1

Thyroid disease screening with ultrasound can have a dramatic effect on the detection of thyroid nodules. A 15-fold increase in the incidence of thyroid cancer occurred in South Korea after the introduction of a national cancer screening program in 1999, with the incidence rate in regions increasing in direct proportion to the percentage of screened people.3 Consequently, it is inappropriate to compare the data from the Fukushima screening program with cancer registry data from the rest of Japan where there is, in general, no such large-scale screening. The proper comparison is between different screened areas within Fukushima Prefecture, since significant radioactive contamination from the accident was confined to a relatively small part of the prefecture.

There is no statistically discernible difference in thyroid cancer prevalence between the low, intermediate, and high contamination areas of Fukushima Prefecture. The prevalence ratio for the highest to lowest contamination areas was 1.08 (95% confidence interval [CI]: 0.60, 1.96), and the highest prevalence was seen in the area with an intermediate level of contamination (prevalence ratio = 1.21 [95% CI: 0.80, 1.82]). Furthermore, the measured levels of radioactivity in thyroids in Fukushima Prefecture were far lower4 than would be needed to elevate cancer rates as much as Tsuda et al.1 claim.

The situation in areas of the former USSR heavily contaminated following the Chernobyl accident in 1986 is of relevance here: in these areas, many children received high thyroid doses (much higher than those following the Fukushima accident) and there is a clear and large excess of thyroid cancer in this group. The thyroids of 13,127 Ukrainians, 17 years old or younger at the time of the accident, were screened between 1998 and 2000.5 Based on this study, 105 (95% CI: 30, 258) background cases of thyroid cancer would be expected from the first screening in Fukushima prefecture.6 The good agreement between this point estimate and the number of 112 cases that has been detected up to the end of March 2015 in Fukushima Prefecture1 does not permit the inference that an effect of radiation exposure has been demonstrated. A more plausible conclusion is that the screening program is finding an anticipated increase in thyroid cancer detection across the prefecture.

Richard Wakeford

The University of Manchester

Manchester, United Kingdom

Centre for Occupational and Environmental Health

Institute of Population Health

Faculty of Medical and Human Sciences

The University of Manchester

Manchester, United Kingdom

Anssi Auvinen

University of Tampere

Tampere, Finland

R. Nick Gent

Public Health England

Chilton, United Kingdom

Peter Jacob

Helmholtz Zentrum München

Munich, Germany

Ausrele Kesminiene

International Agency for Research on Cancer

Lyon, France

Dominique Laurier

Institute for Radiological Protection and Nuclear Safety

Fontenay aux Roses, France

Joachim Schüz

International Agency for Research on Cancer

Lyon, France

Roy Shore

Radiation Effects Research Foundation (Retired)

Hiroshima, Japan

Linda Walsh

Federal Office for Radiation Protection

Oberschleissheim, Germany

Wei Zhang

Public Health England

Chilton, United Kingdom


1. Tsuda T, Tokinobu A, Yamamoto E, Suzuki E.. Thyroid cancer detection by ultrasound among residents ages 18 years and younger in Fukushima, Japan: 2011 to 2014. Epidemiology. 2016;27:316–322
2. World Health Organization. Health Risk Assessment from the Nuclear Accident after the 2011 Great East Japan Earthquake and Tsunami Based on a Preliminary Dose Estimation. 2013 Geneva, Switzerland WHO Press
3. Ahn HS, Kim HJ, Welch HG.. Korea’s thyroid-cancer “epidemic”: screening and overdiagnosis. N Engl J Med. 2014;371:1765–1767
4. Nagataki S, Takamura N, Kamiya K, Akashi M.. Measurements of individual radiation doses in residents living around the Fukushima Nuclear Power Plant. Radiat Res. 2013;180:439–447
5. Tronko MD, Howe GR, Bogdanova TI, et al. A cohort study of thyroid cancer and other thyroid diseases after the Chernobyl accident: thyroid cancer in Ukraine detected during first screening. J Natl Cancer Inst. 2006;98:897–903
6. Jacob P, Kaiser JC, Ulanovsky A.. Ultra sonography survey and thyroid cancer in the Fukushima Prefecture. Radiat Environ Biophys. 2014;53:391–401
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