Title: Misrepresented risk of thyroid cancer in Fukushima
Abstract: The possibility of a causal association between radiation exposure and thyroid cancer in Fukushima, Japan after the 2011 nuclear disaster is a controversial topic. In The Lancet Diabetes & Endocrinology, Noboru Takamura and colleagues1Takamura N Orita M Saenko V Yamashita S Nagataki S Demidchik Y Radiation and risk of thyroid cancer: Fukushima and Chernobyl.Lancet Diabetes Endocrinol. 2016; 4: 647Summary Full Text Full Text PDF PubMed Scopus (29) Google Scholar prematurely and misleadingly dismiss the radiation effect in attributing cases of thyroid cancer detected in Fukushima as “an effect of screening caused by the use of modern, highly sensitive ultrasound technology”. Takamura and colleagues note that the increase in incidence of thyroid cancer in children in Belarus was seen only 4–10 years after the 1986 Chernobyl accident, and was seen mostly in those aged 0–5 years at the time of the accident. The authors thereby concluded that the 113 cases of thyroid cancer detected in Fukushima during the first screening cycle (October, 2011, to March, 2014), seen mostly in older age groups, were probably due to a screening effect. A more logical conclusion suggests that a similar trend might be seen in Fukushima, 4–10 years after the accident, when such data become available. It is not valid to compare two different post-accident periods (after [Belarus] and during [Fukushima] the first 3–4 years) or different age ranges (0–15 years in Belarus vs 0–18 years in Fukushima). Furthermore, whereas Takamura and colleagues1Takamura N Orita M Saenko V Yamashita S Nagataki S Demidchik Y Radiation and risk of thyroid cancer: Fukushima and Chernobyl.Lancet Diabetes Endocrinol. 2016; 4: 647Summary Full Text Full Text PDF PubMed Scopus (29) Google Scholar declare that Fukushima's low thyroid dose levels were “unlikely to have caused a detectable excess in thyroid cancer within 4 years”, the investigators of an epidemiological analysis of the cancer data from Fukushima2Tsuda 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: 316-322Crossref PubMed Scopus (5) Google Scholar concluded that an excess of thyroid cancer was detected within 4 years of the accident. Takamura and colleagues disregarded the shortcomings of the thyroid dose measurements,3Kim E Kurihara O Suzuki T et al.Screening survey on thyroid exposure for children after the Fukushima Daiichi nuclear power station accident.in: Kurihara O Akahane K Fukuda S Miyahara N Yonai S Proceedings of the 1st NIRS symposium on reconstruction of early internal dose in the TEPCO Fukushima Daiichi nuclear power station accident. National Institute of Radiological Sciences, Chiba2012: 59-66http://www.nirs.go.jp/publication/irregular/pdf/nirs_m_252.pdfGoogle Scholar including a small sample size (1080 vs 360 000 children in the full cohort) and high background radiation levels leading to uncertainties and underestimation. Focus on these doses might overlook potentially higher doses due to individual variation in exposure from behaviour patterns and intake of food and water. Essentially, the thyroid exposure doses of the cancer cases are unknown and the effect is likely to be linear. While high radiation doses have been known to be harmful, more recent evidence within the past 5–10 years points towards increased cancer risks at low doses,4Mathews JD Forsythe AV Brady Z et al.Cancer risk in 680 000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians.BMJ. 2013; 346: f2360Crossref PubMed Scopus (1360) Google Scholar, 5Spycher BD Lupatsch JE Zwahlen M et al.Background ionizing radiation and the risk of childhood cancer: a census-based nationwide cohort study.Environ Health Perspect. 2015; 123: 622-628Crossref PubMed Scopus (5) Google Scholar with no apparent dose threshold. Even if a statistically detectable excess was absent at this timepoint (end of the first screening period [March, 2014]) for the Fukushima population, it does not mean there is not cancer risk due to the accident. I declare no competing interests. I am a member of Physicians for Social Responsibility Radiation and Health Committee. Radiation and risk of thyroid cancer: Fukushima and Chernobyl30 years have passed since the accident at the Chernobyl nuclear power plant in Ukraine, and 5 years have passed since the crisis at the Fukushima Daiichi nuclear power plant. After the Chernobyl disaster, a significant increase in thyroid cancer was reported among children and adolescents exposed to radioactive iodine released at the time of the accident in Belarus, Russia, and the Ukraine.1 On the basis of the experience of Chernobyl, thyroid ultrasound examination is being done within the framework of the Fukushima Health Management Survey. Full-Text PDF Misrepresented risk of thyroid cancer in Fukushima – Authors' replyBeyond Fukushima, substantial increases in thyroid cancer have been reported worldwide.1 The introduction of modern advanced ultrasonography can lead to a massive increase in the detection of small and asymptomatic thyroid cancers.1 In 2014 we reviewed findings of three thyroid ultrasound screening programmes done in Japan and showed that the prevalence of thyroid cancer was 300 per million (Chiba), 1300 per million (Okayama), and 350 per million (Tokyo).2 These results show that the prevalence of thyroid cancer identified with advanced ultrasound techniques in other areas of Japan does not differ from the prevalence during the first cycle of the Fukushima Health Management Survey (386 per million). Full-Text PDF
Publication Year: 2016
Publication Date: 2016-11-22
Language: en
Type: letter
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 3
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