Childhood Thyroid Examinations in the Kanto Hotspot: A Report（Study Period: October 2013 to December 2017）

Similar to that in the Chernobyl nuclear accident, the occurrence of thyroid cancer in children was also feared following the Fukushima nuclear in Japan. Thyroid examination of children residing in the Fukushima Prefecture was performed quickly and nearly 200 cases or suspected cases of thyroid cancer have been reported. However, the thyroid glands of children evacuated from Fukushima and the hotspot area of Kanto have not been screened. Therefore, in response to requests from mothers outside Fukushima Prefecture, we started ultrasound examinations of the thyroid glands of children in October 2013. Since then, examinations have been performed annually until now. This report describes the results of these examinations performed through December 2017. The judgment standards for ultrasound examination of the thyroid gland were as indicated by Fukushima Prefectural University. Briefly, A1 judgment: without nodules or cysts, A2 judgment: with nodules measuring 5.0 mm or less or cysts measuring 20.0 mm or less, B judgment: nodules measuring 5.1 mm or more or cysts measuring 20.1 mm or more, and C judgment: requiring immediate secondary examination. Ultrasound examinations of the thyroid gland were conducted in the presence of family members and parents; in order to correctly convey the findings to the family, the findings were explained while viewing the images on the spot. Thyroid screening was conducted for residents of the Kanto hotspot for four years and a total of 8,171 people were examined. A1, A2, B, and C judgments were observed in 2,089 （25.6%）, 5,969 （73.1%）, 106 （1.3%）, and 7 persons （0.1%）, respectively. Nodules were noted in 226 patients （2.77%）. At the time of the nuclear accident, pediatric thyroid ultrasonography was performed in a total of 7,693 children under 18 years of age. A1, A2, B, and C judgments were observed in 1,922 （25%）, 5,735 （74.5%）, B 34 （0.4%）, and C two people （0.29%）, respectively, and nodules were observed in 125 people （1.62%）. The thyroid examinations were conducted annually by traveling through the hotspot. The number of A2 judgments increased each year, while the number of B judgments did not increase. There was also no increase in the number of C judgments. The results of screening in the Kanto hotspot area revealed that, contrary to the expectation based on reports after the Chernobyl nuclear accident, the frequent occurrence of childhood thyroid cancer was not observed.