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147chap.IIIStruggle Against RadioactivityFUKUSHIMA: Lives on the Linespread to the lymph nodes and lungs at the time of diagnosis as in the case of pediatric papillary thyroid cancer in particular, the vast majority of pediatric patients with thyroid cancer have a good long-term prognosis when appropriately treated5). The prognosis of thyroid cancer, particularly differentiated cancer, is associated with age and becomes less favorable when the patient is older. In the TNM classification by UICC, the cancer staging for differentiated thyroid cancer in patients aged ≥45 years ranges from stages I through IV, but there are only stages I and II for those under the age of 45 years. This is because of their better prognosis, and distant metastases are classified as stage II while all others are classified as stage I3). Furthermore, undifferentiated cancer grows rapidly, having a very poor prognosis, unlike the differentiated cancer. In addition, this cancer is rare in patients <50 years of age. Taking these points into consideration, pediatric thyroid cancers are considered to have favorable prognoses. It is also known that some thyroid cancers are induced by radiation.Characteristics of the Ultrasound Thyroid ExaminationWhen performing thyroid examinations on pediatric populations, the use of computed tomography or scintigraphy should be limited because they may increase unnecessary radiation exposure. Ultrasound imaging, on the other hand, is noninvasive and thus appropriate for pediatric thyroid screening examination. Ultrasound images are relatively easily obtained by placing the probe on the neck region. However, visualization may differ depending on the skills of each examiner. Therefore, a highly experienced examiner is required for this examination. Thanks to the advances in ultrasound instruments, even nodules approximately 1 mm in size can be visualized. The ultrasound was previously used to diagnose the presence or absence of a condition. If an abnormality such as a nodule was found, the patient was sent to a specialist who would then perform a fine-needle aspiration biopsy, and excise multiple microcarcinomas of a few millimeters in size. More recently, however, the ultrasound has also been used for qualitative diagnoses, and to a certain degree a diagnosis could be made even without a fine-needle aspiration biopsy. For cancers such as that of the mammary gland, detecting almost impalpably small cancers can contribute to a better survival rate. In contrast, exploring small thyroid cancers and excising them is not our main objective because as much as 36% potential cancers (latent cancers) were found in the thyroid gland during autopsy, and most of them were microcancers <10 mm in size5).Implementation of the Primary ExaminationThe Fukushima health management survey was launched in July 2011, starting with a basic survey using questionnaires. The thyroid gland examination as one of the detailed surveys was carried out on weekends and holidays between October 9 and November 13 of the same year at Fukushima Medical University Hospital. Of the roughly 4,000 target residents of Iitate Village, Namie Town, and Yamakiya District in Kawamata Town, 3,765 residents sought to take part in this examination. Subsequently, from November 14 to December 16, on Monday through Friday, the visiting examinations were performed in Kawamata Town and Minami-soma City. A total of 10,677 residents have undergone these examinations, of which 1,977 were from Kawamata Town excluding Yamakiya District and 8,700 were from Minami-soma City. By the end of last year, the total number reached 14,442. From January 2012 until March 23, 2012, a total of 28,099 residents participated in the study from the remaining government-designated evacuation zones of Date City, Tamura City, Hirono Town, Naraha Town, Tomioka Town, Kawauchi Village, Okuma Town, Futaba Town, and Katsurao Village (22,614 of them were the residents of Fukushima municipalities while 5,485 of them were evacuees outside the prefecture, as of November 21, 2011). A total of 38,114 residents out of the 47,766 target population, consisting of 10,274 in Date City, 6,180 in Tamura City, and 7,218 in the other evacuation zones participated, with a 79.8% participation rate (Table 1). Most of the participants from Iitate Village, Kawamata Town, Date City, or Tamura City resided within Fukushima Prefecture while as many as 22%–33% of participants from Minami-soma City, Namie Town, and other evacuation zones were from other prefectures. The breakdown of the participation rate by age group was as follows: 77.5% between 0–5 years of age, 84.9% between 6-10 years of age, 84.5% between 11–15 years of age, and 68.7% aged ≥16 years, with the highest rate seen in the 6–15-year-old age group, because many of them were tested at schools. The children between 0–5 years of age, for whom performing examination was suspected to be difficult even by the specialists, had a nearly 80% participation rate, and all of them were successfully examined.Primary Study Results NoticeBefore being sent out by mail, results of the primary

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