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Comment & Response
June 13, 2019

Incidence of Thyroid Cancer Among Children and Young Adults in Fukushima, Japan—Reply

Author Affiliations
  • 1Department of Radiation Health Management, Fukushima Medical University, Fukushima, Japan
  • 2Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima, Japan
  • 3National Institute of Public Health, Saitama, Japan
  • 4Hiroshima University, Hiroshima, Japan
JAMA Otolaryngol Head Neck Surg. 2019;145(8):770. doi:10.1001/jamaoto.2019.1102

In Reply In our observational study,1 we comprehensively assessed the characteristics of thyroid cancer screened by ultrasonography among children and young adults with 2 rounds of examination during the first 5 years after the 2011 Fukushima Daiichi nuclear power station accident.

The article by Takahashi et al2 that Suzuki et al referred to was a simulation study of anticipated childhood and adolescent thyroid cancer cases in Japan that used a cancer progression model based on the National Cancer Registry. However, Figure 1 in our study was not based on the simulation model but on the exact detected cases in the thyroid examinations, the values of which were adjusted for the number of participants in each age group at the time of the accident. Suzuki et al highlighted the following 2 concerns: (1) goodness of fit should be shown and (2) detectable incidence function J(s) should be specifically checked to see whether or not it is dependent on age with evidence. Although these factors are significant for further analysis based on the simulation model, a recent analysis showed that ultrasonography screening–detected thyroid cancers do not have a linear progression but fall into a growth arrest in many young patients.3 Thus, future studies will be conducted to run simulation models based on theoretically reasonable tumor growth patterns of thyroid cancer in young patients based on ultrasonographic observation data from the Fukushima cohort.

Akabayashi et al mentioned that the data corresponded to the baseline by the ultrasonography thyroid screening for children and the young adult population in Japan and highlighted the following 2 concerns for this study design: (1) the gradually decreasing participation rate over time and (2) the lack of large-scale controls. The participation rate from the first to the third round suggested by them was the value in the primary examination. Nevertheless, the confirmatory examinations of the third round of examination to confirm the diagnoses of the thyroid nodules are still ongoing. Recently, an international multidisciplinary expert group assessed the scientific evidence to formulate recommendations about long-term strategies for thyroid health monitoring after a nuclear power plant accident and published their findings in the International Agency for Research on Cancer Technical Publication.4 They developed 2 recommendations as follows: (1) against population thyroid screening after a nuclear accident and (2) considering offering a long-term thyroid monitoring program for higher-risk individuals after a nuclear accident. In the Fukushima situation, it is unethical to set a control group and induce an increased participation rate against the protocol of voluntary participation. To assess the health effects of low-dose exposures within the limits of the ethical conduct of such research, the ideal program would be initially conducted on a voluntary basis, with adequate information on both the benefit and harm of screening, and the program would be based on a conservative clinical examination in which only suspicious cancer cases are referred for ultrasonography to prevent overdiagnosis.5 Given that the risk for radiation-induced thyroid cancer is highest among children who are younger at the time of exposure, the comparison of age-group incidence between the second and third or subsequent examinations should help elucidate the effects of radiation on health.

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Article Information

Corresponding Author: Akira Ohtsuru, MD, PhD, Department of Radiation Health Management, Fukushima Medical University, 1 Hikarigaoka, Fukushima 960-1295, Japan (ohtsuru@fmu.ac.jp).

Published Online: June 13, 2019. doi:10.1001/jamaoto.2019.1102

Conflict of Interest Disclosures: None reported.

References
1.
Ohtsuru  A, Midorikawa  S, Ohira  T,  et al.  Incidence of thyroid cancer among children and young adults in Fukushima, Japan, screened with 2 rounds of ultrasonography within 5 years of the 2011 Fukushima Daiichi nuclear power station accident.  JAMA Otolaryngol Head Neck Surg. 2019;145(1):4-11. doi:10.1001/jamaoto.2018.3121PubMedGoogle ScholarCrossref
2.
Takahashi  H, Takahashi  K, Shimura  H,  et al.  Simulation of expected childhood and adolescent thyroid cancer cases in Japan using a cancer-progression model based on the National Cancer Registry: application to the first-round thyroid examination of the Fukushima Health Management Survey.  Medicine (Baltimore). 2017;96(48):e8631. doi:10.1097/MD.0000000000008631PubMedGoogle ScholarCrossref
3.
Midorikawa  S, Ohtsuru  A, Murakami  M,  et al.  Comparative analysis of the growth pattern of thyroid cancer in young patients screened by ultrasonography in Japan after a nuclear accident: the Fukushima Health Management Survey.  JAMA Otolaryngol Head Neck Surg. 2017;144(1):57-63. doi:10.1001/jamaoto.2017.2133PubMedGoogle Scholar
4.
IARC Expert Group on Thyroid Health Monitoring after Nuclear Accidents.  Thyroid Health Monitoring After Nuclear Accidents. IARC Technical Publication No. 46. Lyon, France: International Agency for Research on Cancer; 2018.
5.
SHAMISEN. ST1 - Lessons learned from dosimetric and health screening, evacuation and health surveillance: executive summary. https://www.irsn.fr/FR/Actualites_presse/Actualites/ Documents/IRSN_Shamisen-recommendation-guide_201709.pdf. Accessed March 14, 2019.
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