26 Thyroid Cancer Cases Confirmed in Fukushima Children: Preliminary Results of FY2011-2013 Thyroid Ultrasound Examination

Thirteenth Prefectural Oversight Committee convened on November 12, 2013, releasing the results of the latest thyroid examination as part of the prefectural health management survey.

Please refer to this post for complete translation of the full results.  

A summary of the results is provided below:

Total number of children examined as of September 30, 2013: 289,960

Total number of children whose initial examination results are confirmed: 225,537
(up to the August 23rd, 2013 examination)
     Assessment A1  121,525 (no nodules or cysts found)
     Assessment A2  102,453 (nodules 5.0 mm or smaller or cysts 20.0 mm or smaller)
     Assessment B     1,558 (nodules 5.1 mm or larger or cysts 20.1 mm or larger)
     Assessment C         1 (requiring immediate secondary examination)

Secondary examination includes more detailed thyroid ultrasound, blood and urine tests, and fine-needle aspiration biopsy if warranted.
      1,559 are eligible for secondary examination
      1,148 have actually undergone secondary examination
        897 finished the secondary examination

In summary, as of September 30, 2013, 26 thyroid cancer cases are confirmed and 32 have suspicious biopsy results. (As of July 31, 2013, there were 18 confirmed and 25 suspected cases).

During the committee meeting, Shinichi Suzuki, the head of the thyroid examination, mentioned that one of the 26 confirmed cancer cases was not papillary thyroid cancer: This case is undergoing cytological reevaluation to determine the subtype of thyroid cancer.

During the press conference following the committee meeting, no information was given, as to the details of individual cancer cases, such as the presence of lymph node metastasis or the type of surgery done.

Shinichi Suzuki maintains that this thyroid examination was originally initiated to assess the baseline thyroid condition of Fukushima children, as there is no such epidemiological data available in Japan, with an understanding that it was not possible to obtain pre-exposure data. It is being conducted on an assumption that the effect of radiation exposure would not be obvious for at least four years after exposure, as was seen after the Chernobyl accident.

If these cancer cases were indeed screening effects, similar malignancy would have to be expected in other parts of Japan. As for the thyroid survey conducted by the Ministry of Environment in Aomori, Yamanashi and Nagasaki Prefectures, widely recognized as a comparison study, no cancer data is available from the cases of thyroid ultrasound abnormalities detected. Also it is not age- and gender-matched, and there is a question about the possibly uneven quality of ultrasound examination itself between the two studies. The MOE spokesperson indicated that abnormal cases are undergoing further examination, and more data might become available for comparison.


Alfred Körblein said...

Yuri, is there no way to determine the spontaneous incidence rate of thyroid cancer before Fukushima from cancer registry data?

@YuriHiranuma said...

Alfred, what is available is this:
Cancer Incidence Rate by Age and Site(2007) p.72 (per 100,000)

There is no "mass screening" with thyroid ultrasound in Japanese pediatric population that was ever done.

Cindy Folkers said...

Hi, Yuri,

you say "If these cancer cases were indeed screening effects, similar malignancy would have to be expected in other parts of Japan." Are other children in Japan, who were not exposed to radioactive iodine being screened using ultrasound? Say in Okinawa where we might be able to be sure they were not as exposed? Thanks.

@YuriHiranuma said...

Hi Cindy,

As mentioned in the post, the Ministry of the Environment (MOE) conducted a thyroid survey in three prefectures, Aomori, Yamanashi, and Nagasaki. It is unclear why these prefectures were selected. The results are available here in English: http://www.env.go.jp/en/headline/headline.php?serial=1933.
More detailed results including the size distribution can be found here (in Japanese): https://www.env.go.jp/chemi/rhm/attach/rep_2503a_full.pdf.

The MOE survey had a relatively larger number of female and a smaller number in age 3-5. It did not include children below age 3 as in the Fukushima survey. Besides, it is not clear if those three prefectures can present a good control group.

There are other civic groups conducting thyroid ultrasound examination in various locations, but I have not heard of any in Okinawa yet.

Related posts:

Subir said...

Good info on thyroid cancer

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