Seventeen More Confirmed Cases: 50 Fukushima Children with Thyroid Cancer

Fifteenth Prefectural Oversight Committee for Fukushima Health Survey convened on May 19, 2014, releasing the results of the latest thyroid examination. ("Fukushima Health Survey" was formerly called "Fukushima Health Management Survey").

Official English translation of the results is available here.

The initial round of thyroid examination finished as of March 31, 2014, although not all the secondary examinations have been completed. The second round of thyroid examination, testing everyone again beginning with areas exposed to higher radiation doses, has already begun, but its results are not available yet.

A summary of the results is provided below:

Total number of children examined as of March 31, 2014: 295,511

Total number of children whose initial examination results are confirmed: 287,056
(Up to the February 21, 2014 examination)
     Assessment A1  148,182 (51.6%) (no nodules or cysts found)
     Assessment A2  136,804 (47.7%) (nodules 5.0 mm or smaller or cysts 20.0 mm or smaller)
     Assessment B     2,069 (0.7%) (nodules 5.1 mm or larger or cysts 20.1 mm or larger)
     Assessment C         1 (0.0%) (requiring immediate secondary examination)

Initial examination progress status

Number and proportion of nodules and cysts

Secondary examination includes more detailed thyroid ultrasound, blood and urine tests, and fine-needle aspiration biopsy if warranted.

      2,070 are eligible for secondary examination
      1,754 have actually undergone secondary examination
      1,598 finished the secondary examination

Secondary examination progress status

Summary of fine-needle aspiration biopsy results (as of March 31, 2014)

In summary, there were 17 more cancer cases confirmed since the last report on February 7th, 2014. 

The total number of cases confirmed or suspected of cancer is 90. Of these, 51 had surgeries as of March 31, 2014 and 1 turned out to be a benign nodule, 49 were confirmed to be papillary thyroid cancer, and 1 still has no confirmed cytological diagnosis but listed as poorly differentiated thyroid cancer. (The total number of cases confirmed or suspected of cancer is often reported as 89 in news report, excluding the case confirmed to be benign). 

Shinichi Suzuki, a Fukushima Medical University professor who is in charge of thyroid examination, said the single case suspected of poorly differentiate thyroid cancer could not be confirmed yet by consulting pathologists due to the evolving international standards for the diagnostic guideline for poorly differentiated thyroid cancer.

Of the total number of 89 confirmed and suspected cases, excluding one case which turned out to be a benign nodule, 50 are confirmed thyroid cancer cases and 39 have cytological biopsy results suspicious of cancer. As of February 7th, 2014, there were 33 confirmed and 41 suspected cases of thyroid cancer: 17 of 41 suspected cases were confirmed with surgery, while 15 more cases had cytological biopsy results suspicious of cancer as the secondary examination progressed. (1,598 of 2,070 eligible completed the secondary examination as of March 31, 2014. This means there is a potential for more cancer cases diagnosed for the initial round of thyroid examination. 

As usual, no information was offered such as the type of nodules and also details of each surgical case which, as part of regular medical care, are considered beyond the scope of the screening and thus inaccessible to the Health Survey team. 

Suspected cases are not always immediately scheduled for surgery. With 47 of the 89 confirmed/suspected cases being over 18 years of age at the time of the secondary examination, some opt to schedule the surgery at a more convenient time, while under observation. (Incidentally, once they turn 18, they no longer have free medical care promised to Fukushima children, and their medical care takes place under the national health insurance with co-payment required. This adds an extra burden to patients and families).

Below is a reference table showing the 2010 thyroid cancer incidence rate per 100,000 in Japan, compiled from National estimates of cancer incidence based on cancer registries in Japan (1975-2010) on the website of Center for Cancer Control and Information Services, National Cancer Center, Japan. Due to an intense interest, domestically and internationally, in the pediatric thyroid cancer occurrence in Japan, the tables focused on the relevant age groups, including the age 20-24 group as some who were younger than age 18 at the time of the accident are now moving into this age category.

Note: The table shows “incidence,” representing the rate of occurrence of new cases in a given period. On the other hand, Fukushima thyroid examination is mass screening, which yields “prevalence,” the proportion of the total number of cases to the total population.

It is important to note that incidence and prevalence are not directly comparable, so the incidence rates shown above are only a relative measure of comparison.

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