Secondary Logo

Associations Between Childhood Thyroid Cancer and External Radiation Dose After the Fukushima Daiichi Nuclear Power Plant Accident

Ohira, Tetsuya; Takahashi, Hideto; Yasumura, Seiji; Ohtsuru, Akira; Midorikawa, Sanae; Suzuki, Satoru; Matsuzuka, Takashi; Shimura, Hiroki; Ishikawa, Tetsuo; Sakai, Akira; Yamashita, Shunichi; Tanigawa, Koichi; Ohto, Hitoshi; Kamiya, Kenji; Suzuki, Shinichifor the Fukushima Health Management Survey Group

doi: 10.1097/EDE.0000000000000839
Letters
Free
SDC

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Epidemiology, Fukushima Medical University School of Medicine, Fukushima, Japan, teoohira@fmu.ac.jp

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, National Institute of Public Health, Saitama, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Public Health, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Radiation Health Management, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Radiation Health Management, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Otorhinolaryngology, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Laboratory Medicine, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Radiation Physics and Chemistry, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Department of Radiation Life Sciences, Fukushima Medical University School of Medicine, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan

Radiation Medical Science Center for the Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan, and, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan

Department of Thyroid and Endocrinology, Fukushima Medical University School of Medicine, Fukushima, Japan

Supported by the National Health Fund for Children and Adults Affected by the Nuclear Incident for design and conduct of the study.

The authors report no conflicts of interest.

Back to Top | Article Outline

To the Editor:

In 2011, the Great East Japan Earthquake and subsequent tsunami hit the Fukushima Daiichi Nuclear Power Plant, causing it to release radioactive elements. Six months later, Fukushima Prefecture started thyroid gland examinations to determine the effects of radiation on incidence of thyroid cancer among residents younger than 18 years.1 We reported that there was no pattern of association between the geographical classification determined by the distribution of municipalities’ external radiation doses and the prevalence of thyroid cancer among the participants in the first 4-year survey.2 However, the broad classification (only three areas) may have combined different radiation dose municipalities. We therefore reanalyzed the associations between extra radiation doses and the prevalence of thyroid cancer using the final data from the first 4 years of thyroid ultrasound examinations.

Subjects were inhabitants aged between 0 and 18 on March 11, 2011 in Fukushima Prefecture. From October 2011 through April 2015, 300,473 subjects (81.7%) were examined as part of the Fukushima Health Management Survey.1 The Ethics Committee of the Fukushima Medical University approved this study (#1318). Written informed consent was obtained from parents of surveyed children. Ultrasonography was used for thyroid gland examinations.1 , 3 Secondary confirmatory examinations were recommended for 2,293 participants, and 2,090 (91.1%) were completed by the end of March 2017. Five hundred forty-seven (26.2%) underwent fine-needle aspiration cytology. One hundred sixteen participants had nodules classified as suspicious or malignant by fine-needle aspiration cytology, with 102 receiving surgical treatment. Finally, 101 participants were diagnosed with thyroid carcinoma. We estimated individual external doses by digitizing behavior data and comparing against computations of daily gamma ray dose rate maps drawn after the accident,4 and the distribution of external radiation doses was highly right-skewed.4 Among 300,473 participants, 129,321 had data on their estimated individual radiation doses. We calculated the proportion of residents who received an external radiation exposure of ≥1 mSv in each municipality in Fukushima (59 municipalities) based on the data of individual radiation dose, and then classified the 59 municipalities into quintiles according to the order of the proportion, as shown in Figure 1. Further, we classified the participants having individual radiation doses (56 with cancer and 129,265 without cancer) into quintiles according to radiation dose. The odds ratios (ORs) and 95% confidence intervals (CIs) of thyroid cancer were calculated using logistic regression models adjusted for age, sex, and the duration from accident to examination.

Figure 1

Figure 1

The adjusted ORs and 95% CIs for thyroid cancer according to the external radiation doses are presented in Figure 1. Compared with the lowest dose area (group E), age- and sex-adjusted ORs (95% CIs) for groups A, B, C, and D were 0.95 (0.48–1.88), 1.44 (0.75–2.75), 1.05 (0.53–2.09), and 1.08 (0.58–2.01), respectively (P for trend = 0.69). From the associations with the quintiles of individual extra radiation doses, the age- and sex-adjusted ORs (95% CI) of thyroid cancer for Q1 (highest: median value, 1.9 mSv), Q2 (high middle: 1.3 mSv), Q3 (middle: 0.7 mSv), and Q4 (low middle: 0.3 mSv) quintiles, compared with Q5 (lowest: 0.2 mSv), were 0.59 (0.24–1.47), 0.73 (0.33–1.60), 0.93 (0.45–1.93), and 0.55 (0.24–1.26), respectively (P for trend = 0.52).

Regional and individual differences in external radiation dose were not associated with thyroid cancer prevalence among children in the 4 years after the nuclear power plant accident. We could not evaluate internal radiation exposure, which was closely associated with thyroid cancer among children in Chernobyl,5 although the internal exposure to 131I among children in Fukushima was much smaller.6 The highest internal radiation doses were expected to affect residents of Futaba town, Iitate village and Iwaki city, and, allowing for some measurement uncertainty,6 their doses were estimated to be mostly below 30 mSv. When we further calculated the age- and sex-adjusted OR of thyroid cancer for these three highest municipalities compared with the lowest dose area (group E), the OR (95% CI) was only 1.16 (0.60–2.25). However, follow-up surveys should be conducted for several years before any conclusions can be drawn, as the timeframe may be too short to detect all radiation-related thyroid cancers.

Table

Table

Back to Top | Article Outline

ACKNOWLEDGMENTS

The authors thank the staff of the Fukushima Health Management Survey for their important contributions. The findings and conclusions of this article are solely the responsibility of the authors and do not represent the official views of the Fukushima Prefecture government.

Tetsuya Ohira

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Epidemiology

Fukushima Medical University School of Medicine

Fukushima, Japan

teoohira@fmu.ac.jp

Hideto Takahashi

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and National Institute of Public Health

Saitama, Japan

Seiji Yasumura

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Public Health

Fukushima Medical University School of Medicine

Fukushima, Japan

Akira Ohtsuru

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Radiation Health Management

Fukushima Medical University School of Medicine

Fukushima, Japan

Sanae Midorikawa

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Radiation Health Management

Fukushima Medical University School of Medicine

Fukushima, Japan

Satoru Suzuki

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan

Takashi Matsuzuka

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Otorhinolaryngology

Fukushima Medical University School of Medicine

Fukushima, Japan

Hiroki Shimura

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Laboratory Medicine

Fukushima Medical University School of Medicine

Fukushima, Japan

Tetsuo Ishikawa

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Radiation Physics and Chemistry

Fukushima Medical University School of Medicine

Fukushima, Japan

Akira Sakai

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Department of Radiation Life Sciences

Fukushima Medical University School of Medicine

Fukushima, Japan

Shunichi Yamashita

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Atomic Bomb Disease Institute

Nagasaki University

Nagasaki, Japan

Koichi Tanigawa

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan

Hitoshi Ohto

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan

Kenji Kamiya

Radiation Medical Science Center for the Fukushima Health Management Survey

Fukushima Medical University

Fukushima, Japan, and Research Institute for Radiation Biology and Medicine

Hiroshima University

Hiroshima, Japan

Shinichi Suzuki

Department of Thyroid and Endocrinology

Fukushima Medical University School of Medicine

Fukushima, Japan

for the Fukushima Health Management Survey Group

Back to Top | Article Outline

REFERENCES

1. Yasumura S, Hosoya M, Yamashita S, et alFukushima Health Management Survey Group. Study protocol for the Fukushima Health Management Survey. J Epidemiol. 2012;22:375–383.
2. Ohira T, Takahashi H, Yasumura S, et alFukushima Health Management Survey Group. Comparison of childhood thyroid cancer prevalence among 3 areas based on external radiation dose after the Fukushima Daiichi nuclear power plant accident: The Fukushima health management survey. Medicine (Baltimore). 2016;95:e4472.
3. Suzuki S, Suzuki S, Fukushima T, et alComprehensive Survey Results of Childhood Thyroid Ultrasound Examinations in Fukushima in the First Four Years After the Fukushima Daiichi Nuclear Power Plant Accident. Thyroid. 2016;26:843–851.
4. Ishikawa T, Yasumura S, Ozasa K, et alThe Fukushima Health Management Survey: estimation of external doses to residents in Fukushima Prefecture. Sci Rep. 2015;5:12712.
5. Suzuki K, Mitsutake N, Saenko V, Yamashita SRadiation signatures in childhood thyroid cancers after the Chernobyl accident: possible roles of radiation in carcinogenesis. Cancer Sci. 2015;106:127–133.
6. Kim E, Kurihara O, Kunishima N, Momose T, Ishikawa T, Akashi MInternal thyroid doses to Fukushima residents-estimation and issues remaining. J Radiat Res. 2016;57 Suppl 1:i118–i126.
Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.