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 Table of Contents  
LETTER TO EDITOR
Year : 2019  |  Volume : 10  |  Issue : 1  |  Page : 79-80

Comments on "Thyroid nodule prevalence among young residents in the evacuation area after fukushima daichi nuclear accident: Results of preliminary analysis using the official data"


1 Department of Nuclear Medicine, University Hospital Wuerzburg, Oberduerrbacher Str. 6, D.97080 Wuerzburg, Germany
2 WHO International Agency for Research on Cancer, Section of Environment and Radiation, 150 Cours Albert Thomas, 69372 Lyon CEDEX 08, France

Date of Web Publication22-May-2019

Correspondence Address:
Prof. Christoph Reiners
Department of Nuclear Medicine, University Hospital Wuerzburg, Oberduerrbacher Str. 6, D.97080 Wuerzburg
Germany
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jrcr.jrcr_6_19

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How to cite this article:
Reiners C, Kesminiene A, Schüz J. Comments on "Thyroid nodule prevalence among young residents in the evacuation area after fukushima daichi nuclear accident: Results of preliminary analysis using the official data". J Radiat Cancer Res 2019;10:79-80

How to cite this URL:
Reiners C, Kesminiene A, Schüz J. Comments on "Thyroid nodule prevalence among young residents in the evacuation area after fukushima daichi nuclear accident: Results of preliminary analysis using the official data". J Radiat Cancer Res [serial online] 2019 [cited 2019 Dec 7];10:79-80. Available from: http://www.journalrcr.org/text.asp?2019/10/1/79/258721



Dear Sir,

Akiba et al. described an increased prevalence of thyroid nodules detected by ultrasound examination (US) in young residents living in the evacuation zone after the Fukushima nuclear accident as compared to the rest of the region (Relative risk (RR): 1.32; 95% confidence interval: 1.1–1.45),[1] using the Fukushima Health Management Survey database.[2],[3] The expected number of thyroid nodules was derived from a US survey in three distant noncontaminated areas of Japan.[4]

Although the authors concluded that “further studies are necessary to evaluate the scientific significance of present findings,” we have, however, some concerns about the methodology of the comparison and the interpretation of the results.

  • Sensitivity of US to detect nodules: the detection rate of small thyroid lesions strongly depends on the resolution of the US transducer characterized by its transmission frequency in MHz and on the training of the investigator. For epidemiological comparison of nodule prevalence, US probes with identical resolution must be only used when they are performed by skilled investigators using a standardized protocol. Akiba et al. referred to 7.5 MHz as the resolution of the US probes,[1] whereas Suzuki et al. in their study on the Fukushima Health Management Survey [3] explained that US probes with resolution of 10–12 MHz were used. Regrettably, no information is given from both studies about systematic training, quality assurance, and the use of other US modalities as, e.g., color Doppler. Hence, direct comparison of detection rates in the two settings is even more uncertain than described by Akiba et al.[1]
  • The role of iodine: the authors had mistakenly compared iodine supplementation in quantities of nutritional supply with iodine thyroid blocking in case of nuclear reactor emergencies. In the latter case, the quantities of iodine are 500–1000 times higher than the usual daily nutritional iodine supply. It is true that Japan is a country with high nutritional iodine supply for instance seafood and kelp, which prevents goiter and thyroid nodules. However, it is incorrect to claim that iodine supply in evacuated persons does not differ from residents of noncontaminated areas. It is clear from the Fukushima Health Management Survey, that the evacuees had a 1.3–1.6 times higher risk of dyslipidemia, diabetes mellitus, and being overweight compared with the nonevacuees in a prospective analysis.[5] The reasons are manifold, but changes of diet and lifestyle from traditional healthy Japanese food to western-style fast food (containing much less iodine) can play more important role than stated by the authors. In particularly, it could have had an impact on the higher prevalence rate of thyroid nodules in the evacuated area observed during the second-round survey conducted 3–6 years after the accident.
  • Statistical approach and findings: the authors calculated the expected prevalence rates of thyroid nodules based on the data obtained in the three noncontaminated areas. The numbers of examinees, particularly in the youngest age group, were very small and the derived estimates can be therefore not sufficiently stable. In addition, there is no confirmation that the investigators were blinded regarding evacuee's status of the examined subject which could have also contributed to the obtained differences in the results between the evacuated and other areas.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Akiba S, Nandakumar A, Higuchi K, Tsuji M, Uwatoko F. Thyroid nodule prevalence among young residents in the evacuation area after Fukushima Daiichi nuclear accident: Results of preliminary analysis using the official data. J Radiat Cancer Res 2017;8:174-9.  Back to cited text no. 1
  [Full text]  
2.
Suzuki S, Suzuki S, Fukushima T, Midorikawa S, Shimura H, Matsuzuka T, et al. Comprehensive survey results of childhood thyroid ultrasound examinations in Fukushima in the first four years after the Fukushima Daiichi nuclear power plant accident. Thyroid 2016;26:843-51.  Back to cited text no. 2
    
3.
Suzuki S, Yamashita S, Fukushima T, Nakano K, Midorikawa S, Ohtsuru A, et al. The protocol and preliminary baseline survey results of the thyroid ultrasound examination in Fukushima. Endocr J 2015;62:261-8.  Back to cited text no. 3
    
4.
Hayashida N, Imaizumi M, Shimura H, Okubo N, Asari Y, Nigawara T, et al. Thyroid ultrasound findings in children from three Japanese prefectures: Aomori, Yamanashi and Nagasaki. PLoS One 2013;8:e83220.  Back to cited text no. 4
    
5.
Hasegawa A, Ohira T, Maeda M, Yasumura S, Tanigawa K. Emergency responses and health consequences after the Fukushima accident; evacuation and relocation. Clin Oncol (R Coll Radiol) 2016;28:237-44.Dear Sir,  Back to cited text no. 5
    




 

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