FUKUSHIMA Lives on the Line

146Journal of the Fukushima Medical Association Volume 74, Number 5 (24.5)The Results of Thyroid Examinations, Our Goals, and Future ProspectsShin-ichi SuzukiDepartment of Organ Regulatory Surgery, Fukushima Medical University Fukushima Disaster Medicine Coordinating Chief PhysicianClinical Department (in charge of thyroid examinations), Radiation Medical Science Center for the Fukushima Health Management SurveyIntroductionOn March 11, 2011, the Tokyo Electric Power Company's Fukushima Daiichi nuclear power plant suffered major damage after the Great East Japan Earthquake. As a result, a large amount of radioactive material was released to the atmosphere from the damaged plant. Last May, Fukushima Prefecture decided to conduct the Fukushima health management survey. The survey consists of a basic survey and four detailed surveys, one of which is a lifelong ultrasound study of the thyroid glands of children in Fukushima Prefecture between the ages of 0 and 18 years at the time of the accident. A little less than 40,000 participants have already been examined to date. Results of the primary examination have been reported while the secondary examination is currently being carried out. Physicians of the Medical Association may be required to explain or provide some guidance regarding this survey during their routine medical practice. Herein, I would like to explain the outlines of this project, hoping to summarize the information and to promote further understanding of the project.Overview of the Thyroid ExaminationThe subjects selected for the primary examination were approximately 360,000 residents of Fukushima Prefecture (including those who evacueted to other prefectures), who were approximately ≤18 years of age at the time of the earthquake. Ultrasound examination of the thyroid gland is performed. The protocols for further examination are as follows. When the primary examination reveals a nodule of ≥5.1 mm or cyst of ≥20.1 mm (cysts containing a solid area were considered as nodules), a confirmatory secondary examination will be carried out. The participants with unremarkable results who are not selected for the secondary examination will be provided the same primary screening examination 2.5 years later, which will be repeated at 2-year intervals until the age of 20, and then at 5-year intervals afterward. The secondary examination, which is a more detailed confirmatory ultrasound study, determines whether a fine-needle aspiration cytology should be performed, on the basis of the diagnostic procedures by the Committee on Thyroid Terminology and Diagnostic Criteria of the Japan Association of Breast and Thyroid Sonology1), and the ultrasound diagnostic criteria of thyroid nodules (tumors) by the Japan Society of Ultrasound in Medicine2). Furthermore, the blood levels of FT4, FT3, TSH, TgAb, TPOAb, and Tg, as well as the urine iodine levels of all participants will be measured. On the basis of the results of these examinations, participants are recommended to have either a routine follow-up, re-examination and follow-up at the facility for secondary examination, or have treatment such as surgery.Characteristics of Thyroid Cancer, Particularly in ChildrenWith regard to the various types of thyroid cancers, 94%–95% of the cases are differentiated cancers consisting of papillary and follicular thyroid cancer. Such cancers have a 10-year survival rate of 95%–96% and they have the best prognosis among all solid cancers. In contrast, undifferentiated thyroid cancers are rare with an incidence of 2%, and they have one of the worst prognoses among all solid cancers with the average survival period of 6 months3,4). Although there is no definitive epidemiological study conducted regarding pediatric thyroid cancer, it is generally estimated that 1 in 1–2 million children are affected annually. Statistics from the 29th review of Thyroid Surgeries indicate that pediatric thyroid cancer is extremely rare, with 0.1% of the patients aged ≤19 years, and 0.03% of the patients aged ≤14 years4). Children and adolescents with thyroid cancer have much better long-term outcomes than adults. Even when the cancer appears to be advanced, having