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Fukushima Thyroid Examination: 112 Children Suspected (28 Cases) or Confirmed (84 Cases) with Thyroid Cancer--108 from Initial Screening and 4 from Full-Scale Screening

The Seventeenth Prefectural Oversight Committee convened in Fukushima City, Fukushima Prefecture, on December 25, 2014, releasing the latest results of thyroid examination, consisting of Initial Screening or the first-round (originally scheduled to be conducted from October 2011 to March 2014, but actually still ongoing) and Full-Scale Screening or the second-round (beginning April 2014).

An official English translation of the results is available here.

Initial Screening targeted about 368,000 individuals who were age 18 and younger, residing in Fukushima Prefecture at the time of the Tokyo Electric Fukushima Daiichi nuclear power plant accident on March 11, 2011. About 80% of those eligible have undergone the primary ultrasound examination, either in Fukushima Prefecture or in other prefectures where they have relocated to. Full-Scale Screening, to be conducted every 2 years until age 20 and every 5 years after age 20, additionally targets those who were born in the first year after the accident, aiming to examine approximately 385,000 individuals in a 2-year period. 

Notably, there was a leak of information the day before the committee met, pertaining to four cases from Full-Scale Screening discovered to be suspicious of malignancy, as described in this post. These four cases caused quite a shock as Initial Screening, considered to provide a baseline incidence rate from the prevalence rate obtained as a result of the wide-scale screening, supposedly would have detected all the cases with "pre-existing" tumors. These "pre-existing" or "latent" cancers would have been discovered before becoming symptomatic due to screening. (It is important to note that Shinichi Suzuki, a Fukushima Medical University thyroid surgeon in charge of the thyroid examination, has steadfastly declined to provide the number of children--some are now adults, over 3 years after the accident--who might have had subjective symptoms). In other words, the incidence rate from the second-round of screening would be expected to be lower.

The four cases, 3 males (ages 6, 10, and 17 at the time of the accident) and 1 female (age 15 at the time of the accident), were either A1 (2 cases) or A2 (2 cases) in Initial Screening. Suzuki was grilled about whether these might have been missed diagnoses in Initial Screening, both during the committee meeting and the press conference, and he flatly denied such possibilities stating the retrospective review of the ultrasound images did not reveal any missed lesions. This, however, means the tumors newly arose since Initial Screening in at least 2 of the cases previously classified as A1, which by definition had no nodules or cysts. Suzuki refused to provide the tumor diameter and the speed of tumor growth for each of the four individuals, citing that they were no longer considered part of the screening and thus patient privacy overruled any other obligation for information release. 

The male to female ratio of 3:1 is also unexpectedly high, as thyroid cancers are usually more common in females, except as discovered after the Chernobyl accident. However, Suzuki stated that nothing conclusive can be drawn from merely 4 cases, and they would have to keep an eye on the future development. Eventually Suzuki used these 4 cases to emphasized the importance of participating in Full-Scale Screening even though the Initial Screening result was normal, as in A1. 

If Suzuki was at all puzzled by the contradiction presented by the situation, he did not show it. An unexpectedly high prevalence rate of thyroid nodules and cancer detected in Initial Screening has been attributed to the highly sensitive ultrasound equipment picking up very small tumors. Today Suzuki emphasized the limitation of ultrasound as it might not always detect what's there. Also, Suzuki has repeatedly mentioned how slowly thyroid cancers grow. Then why did these 4 cases become detectable in two and a half years or less? It seems as if he is hiding behind "patient privacy" so as not to reveal some inconvenient truths. 

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A summary of results are provided for Initial Screening and Full-Scale Screening.

Initial Screening (October 2011 - ongoing)

Total number targeted: 367,686
Number of participants in primary examination as of October 31, 2014: 296,586
Number with confirmed results as of October 31, 2014: 296, 253

  • A1   152,633 (51.5%) (no nodules or cysts found)
  • A2   141,379 (47.7%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
  • B         2,240   (0.8%) (nodules ≧ 5.1 mm or cysts ≧ 20.1 mm)
  • C                1   (0.0%) (requiring immediate secondary examination)
(Note: Cysts with solid components are treated as nodules).

Number eligible for secondary examination: 2,241
Number of participants in secondary examination as of October 31, 2014: 2,051
Number with confirmed results as of October 31, 2014: 1,985
Number of fine-needle aspiration biopsy (FNAB) as of October 31, 2014: 519
Number suspicious or confirmed of malignancy: 109 (often referred to as 108, excluding the case of benign nodule)
Number undergoing surgery as of October 31, 2014: 85
  • 1 benign nodule
  • 81 papillary thyroid cancer
  • 3 poorly differentiated cancer

Full-Scale Screening (April 2014 - March 2016)

Total number targeted: 220,000 in FY2014 (about 385,000 total)
Number of participants in primary examination as of October 31, 2014: 82,101
Number with confirmed results as of October 31, 2014: 60,505

  • A1   25,563 (42.2%) (no nodules or cysts found)
  • A2   34,485 (57.0%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
  • B          457   (0.8%) (nodules ≧ 5.1 mm or cysts ≧ 20.1 mm)
  • C              0   (0.0%) (requiring immediate secondary examination)
(Note: Cysts with solid components are treated as nodules).

Number eligible for secondary examination: 457
Number of participants in secondary examination as of October 31, 2014: 248
Number with confirmed results as of October 31, 2014: 155
Number of FNAB as of October 31, 2014: 11
Number suspicious or confirmed of malignancy: 4
Number undergoing surgery as of October 31, 2014: 0


Overall, the number of suspicious or confirmed of malignancy is 113, including a case of post-surgically diagnosed benign nodule. (This number might be referred to as 112, excluding the benign nodule case). Of these, 84 are surgically confirmed as thyroid cancer (81 papillary thyroid cancer and 3 poorly differentiated cancer) and 29 are suspicious of malignancy awaiting surgery, including 5 new cases from Initial Screening and 4 from Full-Scale Screening.

In regards to detailed characteristics of some of the malignant cases, such as metastases, staging, surgical methods, and genetic analysis, refer to this post describing information gathered from various sources. (Such information is not readily provided, as biopsy as well as surgical cases are technically no longer part of the screening and personal data is guarded, almost over-rigorously). 

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Below are translations of some of the tables in the results.

Initial Screening

Table 1. Primary examination results as of October 31, 2014

Table 2. Number and proportion of participants with nodules/cysts as of October 31, 2014

Table 3. Secondary examination: progress and results as of October 31, 2014

Table 4. Results of FNAB

Table 9: Regional comparison of suspicious/malignant cases


Note 10: Excluding duplicate data and unconfirmed results.
Note 11: Excluding unconfirmed results. 
Note 12: The number of FNAB, out of (c), including those who were reclassified as A1 or A2.
Note 13: Excluding one case that was suspected of malignancy but turned out to be benign after surgery.
Note 14: Tamura City, Minamisoma City, Date City, Kawamata Town, Hirono Town, Naraha Town, Tomioka Town, Kawauchi Village, Okuma Town, Futaba Town, Namie Town, Katsurao Village and Iitate Village
Note 15: Fukushima City, Koriyama city, Shirakawa City, Sukagawa City, Nihonmatsu City, Motomiya City, Koori Town, Kunimi Town, Otamamura Village, Kagamiishi Town, Tenei Village, Nishigou Village, Izumizaki Village, Nakajima Village, Yabuki Town, Tanagura Town, Yamatsuri Town, Hanawa Town, Samegawa Village, Ishikawa Town, Tamakawa Village, Hirata Village, Asakawa Town, Furudono Town, Miharu Town, and Ono Town
Note 16: Iwaki City, Soma City, Shinchi Town
Note 17: Aizuwakamatsu City, Kitakata City, Shimogo Town, Hinoemata Village, Tadami Town, Minamiaizu Town, Kitashiobara Village, Nishiaizu Town, Bandai Town, Inawashiro Town, Aizubange Town, Yugawa Village, Yanaizu Town, Mishima Town, Showa Village, and Aizumisato Town

〈Discussion of regional comparison results〉
  • Analysis of 296,253 primary examination participants, excluding duplicates and unconfirmed results, by regions revealed that proportions of B&C tended to increase in the order of "13 municipalities including the evacuation zone," "Nakadori," "Hamadori," and "Aizu region."
  • On the other hand, proportions of suspicious or malignant cases was about the same in "13 municipalities including the evacuation zone," "Nakadori," and "Hamadori," but a little lower in "Aizu region." This is probably because the proportion of those who completed the secondary examination is lower in Aizu region compared to the other areas. 
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Full-Scale Screening

Table 1. Primary examination progress as of October 31, 2014

Table 2. Number and proportion of participants with nodules/cysts as of October 31, 2014

Table 3. Transition from Initial Screening to Full-Scale Screening

Note 1: The upper row shows the number whose Full-Scale Screening results were confirmed, and the lower row the proportion (%).
Note 2: The upper row shows the Initial Screening result in the corresponding diagnostic category in Full-Scale Screening, and the lower row the proportion (%).


Of 60,048 who were classified as A1 (25,563) or A2 (34,485) categories in Full-Scale Screening, 56,204 were also classified as A1 or A2 in Initial Screening. Also, of 457 who were classified as diagnostic category B, 333 were A1 or A2 in Initial Screening.

Also notable is the fact that, of the 3,776 previously unexamined individuals who participated in Full-Scale Screening, 16 were classified in the diagnostic category of B.

Table 4. Secondary examination progress and results as of October 31, 2014

Table 5. Results of FNAB

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