The Great East Japan Earthquake, which occurred on March 11, 2011, and its subsequent Fukushima Daiichi Nuclear Power Plant accident, prompted implementation of the Thyroid Ultrasound Examination (TUE) program as a part of the Fukushima Health Management Survey. The purpose of this program is to support residents of Fukushima Prefecture, and to analyze the health effects of the released radionuclides. Regardless of relatively high participation rates and a well-planned diagnostic flow, it is conceivable that not all thyroid cancer cases can be detected by the TUE program. The aims of the present study were to identify and characterize these "outside" cases, targeting patients at Fukushima Medical University (FMU) Hospital. As of June 30, 2017, we have successfully identified 11 outside cases. These corresponded to 5.7% of the 194 subjects who were identified as having thyroid cancer or suspected thyroid cancer in the TUE program. Although the outside subjects of other institutes were not investigated, the present study may have identified the majority of outside subjects in Japan, considering that FMU Hospital treats a large number of thyroid cancer subjects. Furthermore, the characteristics of the 11 subjects were not different from those of the subjects identified in the TUE program. These findings confirm that the TUE program was able to identify subjects of thyroid cancer adequately and sufficiently.
Keywords: Fukushima Daiichi Nuclear Power Plant accident; Fukushima Health Management Survey; thyroid cancer; thyroid ultrasound examination.