Age distribution of thyroid cancer is an important topic to evaluate the possibility of radiation induced thyroid cancer in Fukushima because comparison of age patterns after exposure in Fukushima and Chernobyl is often used as a criterion of radiation induced thyroid cancer.
S. Suzuki et al. for the Fukushima Health Management Survey (FHMS) concluded that the high prevalence of childhood thyroid cancer detected in the first four years in Fukushima can be attributed to mass screening.1 One reason for this was a striking discrepancy in age distribution of cancer patients in Fukushima within 0-3 years following exposure versus similar data in Ukraine 4-7 years after exposure.2 Their circuitous comparison seems to be because they consider thyroid cancer patients detected during latency period in Chernobyl were not due to radiation. On this assumption, thyroid cancers detected in Fukushima in 0-3 years after exposure can never be radiation induced, as FHMS names the first thyroid examination “Preliminary Baseline Screening”.3 This idea is widely spread and adopted in IAEA 2013 report: thyroid cancers in Fukushima are unlikely to be radiation induced because no case was found in the age of 0–5 years at exposure. 4

They did not argue that thyroid cancers found in Fukushima are not radiation induced because cancers were found in latency (A in Figure), but they took a more circuitous way (B): Because the age pattern of thyroid cancers in Fukushima in 0-3 years after exposure is different from the one of radiation induced cancer of Ukraine in 4-7 years, thyroid cancers in Fukushima in 0-3 years are not radiation induced. The criterion B for radiation induced thyroid cancer seems to be a kind of trick (deception) because it is equivalent to a criterion that thyroid cancers diagnosed in 0-3 years are not due to exposure. FHMS had this conclusion from the beginning of thyroid examination.

Latency period of radiation induced thyroid cancer may distribute and depend on the extent of exposure and patient’s age. Thyroid cancer cases growing quickly in sensitive children of high dose may contribute cases in 0-3 years after exposure. The striking similarity between age patterns during 4 years after exposure in Ukraine and in Fukushima2 suggests similar character of thyroid cancer in both areas.

Those younger than five years at exposure were considered to have the highest risk for thyroid cancer in Ukraine.2 This is not correct because the average numbers of patients per age during 4-7 years for ages 0-4 and 5-18 at exposure were 14.2 and 23.1 cases, respectively. (FIG. 1) The former is 60 % of the latter. Age distributions of thyroid cancer patients after Chernobyl accident are different in three countries, and this shall be examined next. 448

記事を書く前に重要参考リンクを記録しておく。
参考リンク
「福島の甲状腺癌について」福島県立医大鈴木眞一氏国際会議での英語による説明
2016年9月開催「第5回福島国際専門家会議」 S. Suzuki'Correspondence information about the author S. Suzuki
Childhood and Adolescent Thyroid Cancer in Fukushima after the Fukushima Daiichpermalink.phpi Nuclear Power Plant Accident: 5 Years On S. Suzuki Clinical Oncology 2016
Childhood Thyroid Cancer in Belarus, Russia, and Ukraine after Chernobyl and at Present YURI E. DEMIDCHIK, VLADIMIR A. SAENKO, SHUNICHI YAMASHITA
Age Distribution of Childhood Thyroid Cancer Patients in Ukraine After Chernobyl and in Fukushima After the TEPCO-Fukushima Daiichi NPP Accident
Mykola D. Tronko,1 Vladimir A. Saenko, Victor M. Shpak,1 Tetiana I. Bogdanova,1 Shinichi Suzuki,3 and Shunichi Yamashita
山本太郎事務所編集】2017.4.14復興特別委員会「1082人の甲状腺がんについて」
https://www.facebook.com/permalink.php?story_fbid=601566686853048&id=100009991655041&pnref=story
全国で増える「甲状腺の悪性腫瘍」患者
https://www.facebook.com/permalink.php?story_fbid=601389110204139&id=100009991655041&pnref=story
福島・甲状腺がん196人〜「学校検診見直し」検討へ
投稿者: ourplanet
経過観察問題(3):福島県は、《県民健康調査の甲状腺検査で「経過観察」となった2523人の子どものうち「悪性ないし悪性疑い」が発見された症例数を明らかにする義務もなければ、症例数を把握する鈴木眞一教授らの研究プロジェクトとも関わりはない
子ども甲状腺がん基金の崎山比早子さんの講演
多発する小児甲状腺がん、20ミリシーベルト帰還の人権侵害
福島原発事故東電元幹部刑事訴訟第4回公判・崎山比早子講演
甲状腺がん、福島県外の子どもらに重症化傾向 
毎日新聞2018年3月1日
Were those exposed below five years of age at the highest risk for radiation induced thyroid cancer in Chernobyl?
When and where in Chernobyl were those exposed below five years at the highest risk for radiation-induced thyroid cancer?

Age distribution of thyroid cancer is an important topic to evaluate the possibility of radiation induced thyroid cancer in Fukushima because comparison of age patterns after exposure in Fukushima and Chernobyl is often used as a criterion of radiation induced thyroid cancer. Those younger than five years at exposure were considered to have the highest risk for thyroid cancer in Chernobyl.2
S. Suzuki et al. for the Fukushima Health Management Survey conclude that the high prevalence of childhood thyroid cancer detected in the first four years in Fukushima can be attributed to mass screening. [1] The first reason for the conclusion was a striking discrepancy in age distribution of cancer patients in Fukushima within 0-3 years following the accident versus similar data in Ukraine after 4-7 years [2]. What is the meaning of this comparison?
The reason for their strange comparison seems to be because they consider the latency of radiation induced thyroid cancer is 4 years, and therefore thyroid cancer cases diagnosed in 0-4 years following the Chernobyl accident are not related to exposure. If this assumption is accepted, the high prevalence of thyroid cancers detected in Fukushima in 0-4 years after exposure can never be radiation induced. Fukushima Health Management Survey (FHMS) explains the aim of Preliminary Baseline Screening (0-3 years after exposure) of thyroid examination to check the baseline condition of thyroid glands.

However, they did not deny the possibility radiation induced thyroid cancer because they are diagnosed in four years of latency. Instead they took a more complex way: 1st, if thyroid cancers in Fukushima in 0-3 years after exposure were due to radiation, their age pattern should coincide with the radiation induced cancer of Ukraine in 4-7 years after exposure. 2nd, age pattern of thyroid cancer in Fukushima is different from the one in Ukraine after latency period, where those exposed below five years of age have the highest risk. 3rd, the high prevalence of thyroid cancer detected in Fukushima is unlikely to be related to radiation exposure, but can be attributed to mass screening. The three step criterion for radiation induced thyroid cancer seems to be a trick because it is equivalent to a criterion that thyroid cancer cases diagnosed in 0-4 years of latency after exposure are not related to exposure.

In contrast, patients diagnosed in Ukraine after the period of latency, when radiation-induced tumors started to manifest, display principally a different age pattern. A large number of individuals exposed below five years of age, who are at the highest risk for radiation-induced thyroid cancer, have been seen. No such patients have been diagnosed in Fukushima so far.



The authors in [1] and [2] consider that those younger than five years of age had the highest risk for thyroid cancer in Ukraine. This is not correct because the average numbers of patients per age during 1990-1993 (4-7 years after exposure) for ages 0-4 and 5-18 at exposure were 14.2 and 23.1 cases, respectively (Figure 1 in [2]); the former is 60 % of the latter.
They thought that Relationship between the high prevalence of thyroid cancer and exposure of radioiodine in Fukushima is very unlikely because no patients (0-5) years old at exposure have been diagnosed in the first four years. [2] Furthermore, they conclude that the high prevalence of thyroid cancer detected in Fukushima can be attributed to mass screening. Two more reason they adopted are not discussed here.

Yuri E. Demidchi et al. studied the incidence of thyroid cancer in patients of different age groups in Belarus in 1986–2006. [4] The incidence of thyroid cancer per 10,000 in patients of different age groups in Belarus for 20 years (1986–2006) after the Chernobyl accident [4] and the one in Ukraine [5] is shown and analyzed in Figure 1. In Belarus, the children group (0-14 years at diagnosis) shows maximum incidence around 5~11 years after 1986, adolescents (15-19 years) display the maximal incidence around 12~17 years (blue arrow), and then young adults (20-14 years) show steady increase of incidence around 17~20 years (black arrow) as age group (0-4) years old at exposure shifts. Their conclusion that the highest risk for thyroid cancer was found in patients aged 0–4 years at the time of exposure is reasonable for Belarus and in 5~20 years after exposure. [4]
Figure 1B shows the same plot for Ukraine based on Keynote Address in NCRP annual meeting. [5] In Ukraine, incidence of thyroid cancer of children (0-14 years at diagnosis, red) is lowest for 20 years after the accident. The incidence of age group (0-4) years old at 1986, which constitute children group (red) in 0~12 years after 1986, is considered to be low. Adolescents (blue) display a small maximal incidence around 12~17 years (blue arrow), and then young adults show increase of incidence around 17~20 years (black arrow) as age group (0-4) years old at exposure shifts. Hence the incidence for thyroid cancer of age group (0-4) years old at exposure becomes evident and grows only after 12 years from exposure.
Incidence of thyroid cancer of different age groups in Russia [5] was similar to the one in Ukraine.
Age dependence of radiation induced thyroid cancer is found to depend on three countries contaminated variously by Chernobyl accident and time of diagnosis after exposure.

Despite the difference in age distribution of radiation induced thyroid cancer among three countries, Demidchi et al. conclude that the highest risk for thyroid cancer in Chernobyl was found in patients aged 0–4 years at the time of exposure. [4] We found that the highest risk in infants aged 0–4 years at the time of exposure is only the case in Belarus, but not the case in Ukraine or Russia. This idea is widely accepted and used in ex., IAEA 2013 report and reports of Fukushima Health Management Survey.

Age pattern of thyroid cancer of the highest risk for those exposed below five years of age:
When and where in Chernobyl were those exposed below five years of age at the highest risk for radiation-induced thyroid cancer?
Can age distribution of Chernobyl thyroid cancer be a criterion Determine if thyroid cancer is due to radiation exposure of
Comparison of age distribution of thyroid cancer with the one of Chernobyl: Can it help to determine if thyroid cancer is due to radiation exposure?
If thyroid cancers in Fukushima in 0-3 years after exposure were radiation induced, their age pattern should coincide with the one of radiation induced cancer of Ukraine in 4-7 years. The patterns are different, and thyroid cancers in Fukushima are not radiation induced.
Tronko et al.
if thyroid cancers in Fukushima were due to radiation, more cases in exposed preschool-age children would have been expected.
In contrast, patients diagnosed in Ukraine after the period of latency, when radiation-induced tumors started to manifest, display principally a different age pattern. A large number of individuals exposed below five years of age, who are at the highest risk for radiation-induced thyroid cancer, have been seen. No such patients have been diagnosed in Fukushima so far.

Suzuki also considers in [3] that the similar age distributions of thyroid cancer 0-4 years after the accident in Fukushima and in Ukraine is a reason for thyroid cancer in Fukushima are unlikely to be due to radiation exposure. [3]

References
1. Shinichi Suzuki, Satoru Suzuki, Toshihiko Fukushima, Sanae Midorikawa, Hiroki Shimura,1,4
Takashi Matsuzuka, Tetsuo Ishikawa, Hideto Takahashi,1 Akira Ohtsuru, Akira Sakai,
Mitsuaki Hosoya, Seiji Yasumura,1,9 Kenneth E. Nollet,1 Tetsuya Ohira,1,10 Hitoshi Ohto,1 Masafumi Abe,1 Kenji Kamiya, and Shunichi Yamashita, for the Fukushima Health Management Survey, Comprehensive Survey Results of Childhood Thyroid Ultrasound Examinations in Fukushima in the First Four Years after the Fukushima Daiichi Nuclear Power Plant Accident. THYROID
Volume 26, Number 6, 2016 https://www.liebertpub.com/doi/pdfplus/10.1089/thy.2015.0564
2. Tronko MD, Saenko VA, Shpak VM, Bogdanova TI, Suzuki S, Yamashita S 2014, Age distribution of childhood thyroid cancer patients in Ukraine after Chernobyl and in Fukushima after the TEPCO–Fukushima Daiichi NPP accident. Thyroid 24:1547–1548 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4195412/
3.Suzuki, S. Childhood and adolescent thyroid cancer in Fukushima after the Fukushima Daiichi nuclear power plant accident: 5 years on. Clin Oncol (R Coll Radiol). 2016; 28: 263–271
http://www.clinicaloncologyonline.net/article/S0936-6555(16)00002-9/pdf
4. Childhood thyroid cancer in Belarus, Russia, and Ukraine after Chernobyl and at present. Yuri E. Demidchik; Vladimir A. SaenkoII; Shunichi Yamashita, Arq Bras Endocrinol Metab vol.51 no.5 São Paulo July 2007 http://www.scielo.br/pdf/abem/v51n5/a12v51n5.pdf
5. 10th Annual Warren K. Sinclair Keynote Address: Fukushima Nuclear Power Plant Accident and Comprehensive Health Risk Management. Yamashita S. Slide 10 and 15
http://fukushimavoice.blogspot.jp/2013/04/311.html
https://docs.google.com/file/d/0B3fFCVXEJlbvWmJRTlZXSTJhS28/edit


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