IMPE Abstracts

After the accident of Fukushima Daiichi Nuclear Power Plant caused by the Great East Japan Earthquake and the tsunami on March 11, 2011, the Thyroid Ultrasound Examination (TUE) program as a part of the Fukushima Health Management Survey was initiated among subjects aged ≤18 years at the time of the accident in order to support residents of Fukushima Prefecture and to analyze the health effects of the released radionuclides. The first-round survey of the TUE program was undertaken between 2011 and 2013 fiscal years to obtain baseline data, the second-round during 2014-15 and succeeding rounds every two years thereafter. The TUE program consisted of ultrasonographic examinations in both the primary and the secondary confirmatory examinations and, if indicated, fine needle aspiration cytology (FNAC). In the first-round survey the detection rates of thyroid cancer or its suspicion were reported to be much higher than those documented in the cancer registries of Japan. As of March 31, 2022, a total of 284 individuals was found to have thyroid cancer or suspected thyroid cancer cytologically and at least 237 among them underwent surgical treatment. Regarding the effects of radiation most investigators have found no statistically significant increases of thyroid cancer with increased exposure level. This view has also been supported by smaller amounts of released radionuclides and much lower thyroid exposure doses than at the Chornobyl accident, and unincreased occurrence under the age of 5 years at the time of the accident. Concerning the risk of overdiagnosis, i.e. detection of thyroid cancer that would not have become clinically significant throughout life, the criteria for the secondary confirmatory examination and FNAC were developed in an effort to implement its effective countermeasures. This presentation is expected to contribute correct and exact understanding of the current situation of Fukushima.