International Workshop on Radiation and Thyroid Cancer

    Co-organised by the Japanese Ministry of the Environment (MoE), Fukushima Medical University (FMU) and the OECD Nuclear Energy Agency (NEA)

    Shinagawa Prince Hotel, Tokyo, Japan
    21-23 February 2014


    Background

    As with almost any large nuclear reactor accident, the risk of thyroid cancer caused not only by external exposure, but by exposure to iodine-131 (131I) is a key concern. Experience, and some epidemiological studies from the Chernobyl accident demonstrate that large exposures to 131I can cause thyroid cancer in children (0 to 18 years of age), with younger children having more risk than older ones. External exposures that occurred in Hiroshima and Nagasaki also contribute to the current understanding of these risks.

    Because of the release into the atmosphere of significant quantities of 131I from the Fukushima Daiichi reactor accident – about 100 to 500 PBq of 131I, although approximately 1760 PBq in the case of the Chernobyl accident (1 PBq = 1015 Bq) – it was expected that there would be a risk of thyroid cancer in the exposed populations, in particular in exposed children. To address this risk, as well as the risk of other cancers and leukaemia, the Japanese government put a medical surveillance programme in place, shortly after the accident, for the 2 million people living in the Fukushima Prefecture, which includes approximately 360 000 children. According to the Fukushima official report of November 2013, about 239 000 children to date have had preliminary thyroid screening exams, and 1 148 of these children have undergone secondary examinations as part of this programme. The initial ultrasound screening of all children is to be performed within the first three years after the accident, followed by complete thyroid examinations from 2014 onwards. Residents will be monitored regularly thereafter.

    As of November 2013, these thyroid examinations of 238 765 children in Fukushima have resulted in thyroid cancer (papillary carcinoma) being diagnosed in 26 children, all of whom have been cured through surgical intervention. In addition, the examinations identified 59 children with suspected thyroid malignancy.

    The thyroid cancer incidence rate identified thus far in the Fukushima Prefecture seems, at a glance, to be higher than previously reported in the general population of Japan. However, further study is being done on the cancer rate in Japan, not only through the National Cancer Registry, but also using the same ultrasound screening method and protocol used for the residents of the Fukushima Prefecture.

    So far in the Fukushima Prefecture, there is no specific concern about doses from external exposures, even for the thyroid gland. This situation is reflective of the fact that the scientific understanding of thyroid cancer, and in particular the differentiation between spontaneously-occurring and radiation-induced thyroid cancer, is not complete in some areas. Some remaining scientific questions include:

    • The latency period of thyroid cancer, as estimated from the Chernobyl experience, is in the order of four or five years. Russian scientists have reported not seeing any increase in childhood thyroid cancer between 1986 and 1990. The Japanese childhood thyroid cancers in excess of what was seen as the background rate started appearing in 2011, less than one year after the Fukushima Daiichi nuclear accident. As such, the thyroid cancers that have been clearly identified in the children of Fukushima do not seem to fit with the current understanding of the latency period for radiation-induced thyroid cancer in children observed around Chernobyl, but it cannot be completely ruled out at this time that radiation exposure may be the cause of these cancers. More scientific understanding is needed.
    • The World Health Organizati on (WHO) noted in its health risk assessment report that the health statistics dated from 2007 indicated that childhood thyroid cancers were increasing in Japan, such that the current baseline incidence rate of childhood thyroid cancer incidence in Japan may need to be assessed in more detail to be correctly employed in epidemiological studies of the children exposed in the Fukushima Prefecture.
    • To date, approximately 115 000 children from the Fukushima Prefecture have not yet had their thyroids examined. These examinations may change the current statistics.
    • The accident occurred only two years and nine months ago before this data was compiled. According to current knowledge, the risk of contracting thyroid cancer is highest for children exposed at younger ages. As such, all the children of the Fukushima Prefecture, in particular those who were under five years old at the time of the accident, should be closely followed to ensure that any thyroid cancers that do appear will be quickly and appropriately addressed, and that this information can be used to better understand the overall risks to the population.
    • It is most important to clarify the thyroid dose estimates when discussing the cause and effect of radiation-induced thyroid cancers. There is a large difference in such doses between those exposed by the Chernobyl accident and those exposed by the Fukushima Daiichi nuclear accident.

    Workshop objectives

    The objective of this workshop was to develop a state-of-the-art scientific understanding of radiation-induced thyroid cancer, and to share knowledge and experience in this area in order to support the efforts of the Japanese government and the Fukushima Prefecture to enhance public health. Experience in holding effective social dialogues, in order to best understand and appropriately address social concerns, was also a workshop focus.

    Format of the workshop

    The workshop began with a half-day tutorial session, followed by two days of plenary presentations and discussion, including panel sessions summarising the results of each session. A closing panel provided overall results and conclusions from the workshop. A rapporteur provided a workshop summary report and assisted the session co-chairs in summarising key points.

    Working languages

    The working languages of the workshop were in English and Japanese, with simultaneous Japanese to English and English to Japanese translation.

    Video

    Videos of the event have been made available through the Fukushima Medical University.

    Accommodation

    The workshop was held at the main tower of the Shinagawa Prince Hotel in Tokyo.

    Related documents

    Read the press release.

    Speaker biographies

    To learn more about the workshop speakers, please view the document.

    Workshop agenda and presentations

    Download all presentations (141 Mb)

    21 February

    13:00

    Welcome from MoE

    13:05

    Welcome from FMU

    13:10

    Welcome from NEA/CRPPH

    13:15

    Session 1 (tutorial session): Radiation and Thyroid Cancer

    This session presented the scientific understanding of radiation-induced thyroid cancer, an overview of the situation in the Fukushima Prefecture, a review of epidemiology and epidemiological evidence of radiation-induced thyroid cancer, and an overview of thyroid cancer clinical features and treatment schemes.

    Co-Chair: Dr Shigenobu Nagataki (Professor Emeritus, Nagasaki University)
    Co-Chair: Dr Emilie van Deventer (WHO, Switzerland)

    13:25

    1.1 Overview of Radiation-induced Thyroid Cancer

    This paper presented the current state-of-the-art knowledge with regard to radiation-induced thyroid cancer, in terms of risks, detection and treatment. An overview of case studies of thyroid cancer in exposed populations was also included.

    Presenter: Dr Christoph Reiners (Wuerzburg, Germany)

    14:10

    1.2 Overview of the Fukushima Health Management Survey

    This paper provided a broad overview of the FMU Health Management Survey, including all aspects, but focusing principally on thyroid cancer and the screening of children.

    Presenter: Dr Seiji Yasumura (FMU, Japan)

    14:55

    Break

    15:25

    1.3 Overview of Epidemiology of Thyroid Cancer in the Context of the Fukushima Daiichi Nuclear Accident

    This paper presented the epidemiology of thyroid cancer in general, and an outlook of possible future cancer issues related to the Fukushima Daiichi nuclear accident and how to address them with epidemiological methods specifically.

    Presenter: Dr Joachim Schüz (IARC, France)

    16:10

    1.4 Overview of the Clinical Features of Thyroid Cancer

    This paper provided a detailed overview of thyroid cancer in Japan, and clinical trials of active surveillance of micropapillary thyroid cancer.

    Presenter: Dr Miyauchi (Kuma Hospital, Japan)

    16:55

    1.5 Dialogue with Stakeholders in Complex Radiological Circumstances

    This paper presented the stakeholder dialogue experience as it related to discussion of risks and uncertainty in complex situations.

    Presenter: Dr Gaya Gamhewage (WHO, Switzerland)

    17:40

    Discussion and Questions

    The tutorial session co-chairs provided brief summaries of the key points and messages from the session's lectures, and then addressed, with the presenters, any questions that may have arisen from the audience.

    18:00

    Closing of the Tutorial Session

    22 February

    09:30

    Session 2:  Dose Estimations for Those Affected in the Fukushima Prefecture

    This session presented a spectrum of the thyroid dose estimates, and the FMU external dose estimation that had been performed to assist with health management planning for the affected populations.

    Co-Chair: Dr Makoto Akashi (NIRS, Japan)
    Co-Chair: Dr Joanne Brown (PHE CRCE, UK)

    09:40

    2.1 WHO Thyroid Dose Estimation

    This paper provided an overview of the WHO thyroid dose estimation, including its objectives, assumptions, methodology and results.

    Presenter: Dr Emilie van Deventer (WHO, Switzerland)

    10:00

    2.2 Basic Survey External Dose Estimation

    This paper presented the objectives, assumptions, methods and results of the external thyroid dose estimates made for the Fukushima Prefecture residents based on responses to the Fukushima Health Survey.

    Presenter: Dr Tetsuya Ishikawa (FMU, Japan)

    10:20

    2.3 NIRS Estimation of Internal Dose to the Thyroid

    This paper presented the objectives, assumptions, methods and results of the thyroid internal dose estimates made for the Fukushima Prefecture residents and workers at the Fukushima Daiichi nuclear power plant by NIRS.

    Presenter: Dr Osamu Kurihara (NIRS, Japan)

    10:40

    2.4 Estimation of Internal Dose to the Thyroid

    This paper presented the objectives, assumptions, methods and results of the thyroid internal dose estimates made for the public residents of the Fukushima Prefecture by Hirosaki University using innovative approaches.

    Presenter: Dr Shinji Tokonami (Hirosaki University, Japan)

    11:00

    Break

    11:30

    Discussion

    The session chair and rapporteur summarised results and key points, focusing on their relevance to the scientific understanding of population doses, and the current and future risks of thyroid cancers occurring in the children exposed as a result of the Fukushima Daiichi nuclear accident, followed by a general discussion of the session's papers and implications for the future.

    12:00

    Lunch

    13:00

    Session 3: Thyroid Ultrasound Examinations and Thyroid Cancers
    This session was dedicated to the state-of-the-art understanding of thyroid ultrasound examinations, and to the results of examinations of affected residents, and the planned examination of TEPCO workers.

    Co-Chair: Dr Kenji Kamiya (Hiroshima University)
    Co-Chair: Professor Mykola Tronko (Ukraine)

    13:10

    3.1 FMU Thyroid Ultrasound Surveys in the Fukushima Prefecture

    This paper presented an overview of the thyroid ultrasound surveys that were carried out by FMU, including discussions of their objectives, assumptions, methods and results.

    Presenter: Dr Shinichi Suzuki (FMU, Japan)

    13:30

    3.2 FMU Thyroid Ultrasound Surveys in the Yamanashi Prefecture and Review of Latent Thyroid Cancers

    This paper presented an overview of the thyroid ultrasound surveys that were carried out by FMU in a neighbouring prefecture to give an idea of background thyroid cancers in children, including discussions of their objectives, assumptions, methods and results.

    Presenter: Dr Hiroki Shimura (FMU, Japan)

    13:50

    3.3 Childhood Thyroid Cancer in Korea: Results of Recent Surveys

    This paperpresented an overview of the recent survey of background childhood thyroid cancer rates in Korea, focusing on the processes used for assessing thyroid cancer rates, and the public health resources put in place to address survey results.

    Presenter: Jae Hoon Chung, MD, PhD (Sungkyunkwan University School of Medicine, Republic of Korea)

    14:10

    Break

    14:40

    Discussion

    The session chair and rapporteur summarised results and key points, focusing on their relevance to the scientific understanding of ultrasound thyroid survey results in the children exposed as a result of the Fukushima Daiichi nuclear accident, in comparison with other thyroid cancer surveys, followed by a general discussion of the session's papers and implications for the future.

    15:10

    Session 4: Thyroid Cancer Risk Estimates

    Parents in Fukushima are concerned that their children have been exposed, and may contract thyroid cancer. To assist the Japanese government in addressing these concerns, this session focused on the basics of thyroid cancer risk estimation.

    Co-Chair: Dr Kazuo Sakai (NIRS, Japan)
    Co-Chair: Dr Roy Shore (RERF, Japan)

    15:20

    4.1 Ultrasonography Surveys and Thyroid Cancer in the Fukushima Prefecture

    Currently, ultrasonography surveys are being performed for persons residing in the Fukushima Prefecture at the time of the accident, and being up to 18 years old at that time. This paper described the expected thyroid cancer prevalence and future incidence rate in the Fukushima Prefecture under the condition of continued ultrasonography surveys.

    Presenter: Dr Peter Jacob (Helmholtz Zentrum München, Germany)

    15:40

    4.2 Thyroid Dose Estimation for Epidemiological Studies

    A key concern among stakeholders in Fukushima is the health of their children, and in particular the risk of thyroid cancer. This paper described the state of the art in estimating thyroid dose for past and current use in epidemiological studies and risk estimation.

    Presenter: Dr André Bouville (National Cancer Institute, United States)

    16:00

    4.3 Thyroid Cancer Risk to the Embryo and Feotus in the Chernobyl Accident

    This paper discussed the risks to unborn children of contracting thyroid cancer as studied in the populations affected by the Chernobyl accident.

    Presenter: Dr Maureen Hatch (National Cancer Institute, United States)

    16:20

    Discussion

    The session chair and rapporteur summarised results and key points, focusing on their relevance to the scientific understanding of the current and future risks of thyroid cancers occurring in the children exposed as a result of the Fukushima Daiichi nuclear accident, followed by a general discussion of the session's papers and implications for the future.

    17:00

    End of the Second Day

    18:00

    Reception at the Shinagawa Prince Hotel

    23 February

    09:30

    Session 5: Experience with Post-Accident Radiation-induced Childhood Thyroid Cancer

    This session was dedicated to the experience with childhood thyroid cancer in post-accident situations, focusing on approaches to detecting thyroid cancer, and on dose and risk estimation.

    Co-Chair: Dr Yasuhito Sasaki (FMU, Japan)
    Co-Chair: Dr Thierry Schneider (CEPN, France)

    09:40

    5.1 Childhood Thyroid Cancer in A-bomb Survivors

    This paper presented an overview of the thyroid cancers that occurred in A-bomb survivors, including the number and timing of identified thyroid cancers to date, dose estimations, epidemiological estimates of risk, and processes put in place to monitor children for disease.

    Presenter: Dr Roy Shore (RERF, Japan)

    10:00

    5.2 Childhood Thyroid Cancer in Russia Following the Chernobyl Accident

    This paper presented an overview of the thyroid cancers that occurred in Russia following the Chernobyl accident, including screening processes, the number and timing of identified thyroid cancers to date, dose estimations, epidemiological estimates of risk, and processes put in place to monitor children for disease.

    Presenter: Dr Victor Ivanov (Obninsk, Russian Federation)

    10:20

    5.3 Childhood Thyroid Cancer in Ukraine Following the Chernobyl Accident

    This paper presented an overview of the thyroid cancers that occurred in Ukraine following the Chernobyl accident, including screening processes, the number and timing of identified thyroid cancers to date, dose estimations, epidemiological estimates of risk, and processes put in place to monitor children for disease.

    Presenter: Prof. Mykola Tronko (Ukraine)

    10:40

    5.4 Childhood Thyroid Cancer in Belarus Following the Chernobyl Accident

    This paper presented an overview of the thyroid cancers that occurred in Belarus following the Chernobyl accident, including screening processes, the number and timing of identified thyroid cancers to date, dose estimations, epidemiological estimates of risk, and processes put in place to monitor children for disease.

    Presenter: Prof. Yuri Demidchik (Rector of Belarusian Medical Academy of Post-Graduate Education, Republic of Belarus)

    11:00

    Break

    11:30

    5.5 Childhood Thyroid Cancer in the Marshall Islands

    This paper presented an overview of the thyroid cancers that occurred in children living in the Marshall Islands following atomic bomb testing, including the number and timing of identified thyroid cancers to date, dose estimations, epidemiological estimates of risk, and processes put in place to monitor children for disease.

    Presenter: Dr Ashok Vaswani (Department of Energy, United States)

    11:50

    5.6 Thyroid Survey Plans for TEPCO Workers

    This paper presented an overview of TEPCO's plans to perform thyroid surveys of affected workers.

    Presenter: Dr Tomotaka Sobue (Osaka University, Japan)

    12:10

    Discussion

    The session chair and rapporteur summarised results and key points, focusing on the relevance of expertise from other exposure situations to the scientific understanding of the current and future risks of thyroid cancers occurring in the children exposed as a result of the Fukushima Daiichi nuclear accident, followed by a general discussion of the session's papers and implications for the future.

    12:30

    Lunch

    13:30

    Session 6: Stakeholder Involvement Experience

    This session discussed the communication and stakeholder involvement challenges with regard to developing, implementing and assessing complex radiological studies. The importance of, and approaches to stakeholder involvement were also highlighted.

    Co-Chair: Dr Ohtsura Niwa (ICRP, Canada)
    Co-Chair: Dr Michael Siemann (OECD Nuclear Energy Agency, France)

    Michael Siemann gave an introductory presentation on the CRPPH contribution to stakeholder involvement.

    13:50

    6.1 Experience with Stakeholders in Post-accident Situations

    This paper presented the work and experience in terms of stakeholder dialogue projects in Belarus and in Fukushima.

    Presenter: Mr Jacques Lochard (ICRP, Canada)

    14:10

    6.2 Experience from the French Nord-Cotentin Study: Involving Stakeholders in the Planning, Implementation and Assessment of Dose Assessment and Risk Estimate Studies

    This paper presented experience from the Nord-Cotentin study, which investigated a trend towards an excess number of leukaemia cases in the Nord-Cotentin region (France) where, in particular, the La Hague nuclear reprocessing plant is located.

    Presenter: Dr Thierry Schneider (CEPN, France)

    14:30

    6.3 Recovery and Reconstitution Model of Kawauchi Village after the Fukushima Daiichi NPP Accident

    This paper described the process and discussions in planning for the reconstruction of Kawauchi Village.

    Presenter: Dr Noboru Takamura (Nagasaki University, Japan)

    14:50

    Break

    15:20

    6.4 FMU Risk Communication Activities

    This paper presented the stakeholder involvement activities that are being performed by FMU in connection with the Health Management Survey.

    Presenter: Mr Shiro Matsui (Director, PR and Risk-Communication, FMU, Japan)

    15:40

    6.5 The Science of Estimating an Individual's Risk

    Parents are specifically interested in the risk to their children. This paper discussed the scientific aspects of estimating the risk to an individual, its uncertainties and the value that such understanding has for the development of appropriate health follow-up programmes.

    Presenter: Dr Wesley Bolch, University of Florida

    16:00

    Discussion

    The session chair and rapporteur summarised results and key points, focusing on their relevance to the situation in Fukushima and to the management of public health issues, followed by a general discussion of the session's papers and implications for the future.

    16:30

    Summary of the Workshop Results

    The aspects of the papers from all the sessions were summarised, focusing on their relevance to the scientific understanding of the current and future risks of thyroid cancers occurring in the children exposed as a result of the Fukushima Daiichi nuclear accident.

    Panel: chairs, secretariat

    17:00

    Closing Remarks