Fukushima Thyroid Examination October 2017: 154 Surgically Confirmed as Thyroid Cancer Among 193 Cytology Suspected Cases


  • Only 3 suspected/confirmed cases—all in the third round—were newly diagnosed by cytology since the last report. Total number of suspected/confirmed thyroid cancer = 193 (excluding a single case of benign tumor; 115 in the first round, 71 in the second round, and 7 in the third round).
  • Two additional cases of surgery since the last report, one each in the second and the third round: total number of surgically confirmed cancer cases =154 (101 in the first round, 50 in the second round, and 3 in the third round)
  • The second round screening is nearly complete; the final report to be released at the next Oversight Committee or Thyroid Examination Assessment Committee. 
  • A new two-year term begins for newly appointed and returning members of the Oversight Committee as well as the Thyroid Examination Assessment Subcommittee. Surprisingly, Kazuo Shimizu—former Subcommittee Chair—was not even appointed to be on the Subcommittee
On October 23, 2017, the 28th Oversight Committee for Fukushima Health Management Survey convened in Fukushima City, Fukushima Prefecture. Among other information, the Oversight Committee released the latest results (as of June 30, 2017) of the second and third rounds of the Thyroid Ultrasound Examination (TUE).  Official English translation of the results are posted here. Minutes of the proceedings are only released in Japanese, and the transcript of the press conference held immediately after the committee meeting is not officially released. The narrative below includes pertinent information covered during the committee meeting and the press conference.

This Oversight Committee meeting was nearly 2 months overdue. In fact, it was held so late that it could have presented data as of September 30, 2017. But no, all that was presented was rather "old" data as of June 30, 2017, which changed very little in terms of the number of cancer cases compared to the previous data as of March 31, 2017. As schools in Japan go into summer recess in the last one-third of July through the end of August, more cancer cases might be included in the next set of data as of September 30.

Here's the summary of the latest results as of June 30, 2017

Notable new members
With the past term for committee members ending on July 9, 2017, this Oversight Committee opened with some new members. (See the Oversight Committee roster in Japanese here). The most controversial might be Toru Takano, an Osaka University physician researcher who advocates fetal cell carcinogenesis as opposed to multistep carcinogenesis. Takano's hypothesis claims thyroid cancer already exists in childhood which "nicely" explains away a large number of thyroid cancer detected in Fukushima. Takano has called for scaling down Fukushima's TUE in the January 14, 2017 blog post. Takano was recommended to be on the Oversight Committee and the Thyroid Examination Assessment Subcommittee by the Japan Thyroid Association.

As for the new roster of the Thyroid Examination Assessment Subcommittee, Kazuo Shimizu—former Subcommittee Chair—and Fumiko Kasuga—who one might say acted as "conscience" of the Subcommittee—were no longer on it. Takano is joined by Gen Suzuki (recommended by the the Japanese Radiation Research Society) and Tomotaka Sobue (recommended by the Japan Epidemiological Association), both of who have actively participated on various government committees related to health effects of radiation exposure. Kota Katanoda from Division of Cancer Statistics Integration, National Cancer Center appears to have replaced Shoichiro Tsugane. Katanoda and Tsugane have worked on a document submitted to the Subcommittee previously.

Interim report on dose reconstruction studies
Most of the meeting time was spent on presentation by Gen Suzuki on a 3-year interim report of "Comprehensive studies on the dose reconstruction for residents in Fukushima nuclear accidents." Suzuki's presentation slides (in Japanese) can be found here, and an English abstract can be found on pages 437-439 (pages 27-29 of PDF) of the interim report to the Ministry of the Environment. 

"Comprehensive studies" consist of 4 separate studies (English abstract page in parenthesis) on 1) updating source term and atmospheric transport dispersion simulations (page 508), 2) retrospective reconstruction of iodine 131 release through iodine 129 (page 516), 3) dose reconstruction of Fukushima residents in early stages (page 528), and 4) prediction of blood deposition and thyroid accumulation of radioiodine (page 542).

Among loads of complicated pieces of information, the take home message was that estimated doses (external and internal) for a 1-year-old are now (successfully?) reduced to 7% to 69% of estimated doses in the UNSCEAR 2013 report. 

Full-Scale Screening (FSS) (second and third rounds)
To be conducted every 2 years until age 20 and every 5 years after age 20, the FSS began with the second round screening (the first FSS) in April 2014, including those who were born in the first year after the accident. There are 381,256 eligible individuals born between April 2, 1992 and April 1, 2012. As of June 30, 2017, 270,516 (5 more than previously) have actually participated in the primary examination. 

A participation rate of 71.0% is lower than 81.7% from the first round screening. Results of the primary examination have been finalized in 270,515 participants, and 2,227 (1 more than previously) turned out to require the confirmatory examination. 

The confirmatory examination appears to be still ongoing for the second round. Of 2,227 requiring the confirmatory examination, 1,844 (12 more than previously) have participated at a participation rate of 82.8%—lower than 92.9% from the first round screening. So far 1,788 have received the final results including 205 (5 more than previously) that underwent fine needle aspiration cytology (FNAC) which revealed 71 cases suspicious for cancer with no new case diagnosed at this time. 

Confirmation of thyroid cancer requires pathological examination of the resected thyroid tissue obtained during surgery. There has been only 1 additional surgical case in the second round since the last reporting. As of June 30, 2019, 50 underwent surgery and 49 were confirmed to have papillary thyroid cancer. One remaining case was confirmed to have "other thyroid cancer" according to the classification in the seventh revision of Japan's unique thyroid cancer diagnostic guidelines. (A specific diagnosis was not revealed, but it has been reported as a differentiated thyroid cancer that is not known to be related to radiation exposure and it is allegedly neither poorly differentiated thyroid cancer nor medullary cancer). 

The third round screening or the second FSS has covered 138,422 or 41.1% of the survey population of 336,631, which excludes those born in FY1992 and FY1993 who are eligible for the age 25 milestone screening. The primary examination results have been finalized in 123,857 or 89.5% of the participants, revealing 754 (63 more than previously) to require the confirmatory examination. Results of the confirmatory examination have been finalized in 367 of 438 (83.8%) that have been examined. FNAC was conducted in 18 (7 more than previously) individuals, and 3 were newly diagnosed with suspected thyroid cancer (2 females and 1 male). There was 1 new surgical case in the third round.  

A confusing issue on composition of target populations
Conducted every 2 years up to age 20, the TUE transitions at age 25 to "milestone screenings" to be conducted every 5 years. Some residents are beginning to participate in the age 25 milestone screening, and if they have never participated in the TUE, their milestone screening results were added to the second round screening results. Thus the number of the second round screening participants kept increasing even though the screening period technically ended in March 2016. 

However, the third round screening survey population excludes the age 25 milestone screening participants: their results will be tallied up separately.

Also in some cases, confirmatory examinations from the second and third rounds might be simultaneously ongoing, or there could be significant delays in conducting confirmatory examinations due to logistical issues such as the lack of manpower. A two-year screening period originally designed for subsequent rounds of the Full-Scale Screening is essentially spread over a longer time period, overlapping with the next round of screening. A precise interpretation of the results from each round of screening might be nearly impossible.

Participants beyond age 23 dropped from released datasets
As mentioned in the previous section, participants eventually move onto the "milestone screening," every 5 years beginning at age 25. No more than 5 years are to pass between examinations up to age 25. 

The chart shown below is the FSS implementation plan from the third round onward (taken from the blue link in this document on the prefectural website on the TUE for residents). It represents ages of participants by their birth years (leftmost vertical column) at particular years of screening (top row). (Years here are "fiscal years" which run from April 2 of one year to April 1 of next year). Darker blue color denotes the milestone screening participants, yellow the participants in the FSS to bridge the gap before the milestone screening, and lighter blue the regular FSS participants. White color denotes no screening during a given fiscal year.

Based on this chart, the third round excludes those who were born in FY1992 and FY1993 as described earlier. This breaks down to 23- and 24-year-olds from the FY2016 targeted municipalities and 24- and 25-year-olds from the FY2017 municipalities. Thus technically, the third round screening includes only half of 23-year-old residents, with the other half of 23-year-olds and all of 24-year-olds not even screened until FY2018.

Although the milestone screening are being tallied up separately, there has been no talk about when and how—or if—the separate results are to be shared with the Oversight Committee.

From the above chart, it should be noted that as the TUE goes on, the age distribution graph will be skewed to younger ages, and the results will not represent all the residents who were 18 or younger at the time of the accident. The "age-at-exposure" distribution graph shows an X-axis up to age 18, but older age group won't even show up there with each successive round of screening: for the third round, that means all residents who were 17 or 18 and some who were 16 on March 11, 2011. 
Fig 3 Age distribution of suspected/confirmed cancer cases (age at exposure)
Second round on left, third round on right

When looking at the age-at-examination distribution graph as below, the "dropping" of older residents as they turn 23 (some) and 24 is something that should be kept in mind.
Fig 4 Age distribution of suspected/confirmed cancer cases (age at confirmatory exam) 
Second round on left, third round on right

Newly diagnosed cases
The second round: No new case diagnosed.

The third round: Three cases were newly diagnosed by FNAC with suspicion of cancer. One was from the evacuation area, and the other two are from Nakadori, the central part of Fukushima Prefecture. Two are males whose ages-at-exposure were 11 and 12, and one was a female who was age 10 at exposure.

Prior diagnostic status of the cases newly diagnosed with cancer
The second round: Of 71 total cases suspected or confirmed with cancer in the second round, 33 were A1, 32 were A2 (7 nodules, 25 other non-nodular lesions), and 5 were B (at least 2 having undergone the confirmatory examination) in the first round. One remaining case never underwent the first round screening (no information such as age, sex or place or residence, is available regarding this case).

The third round: Of 3 newly diagnosed cases, 1 was A1 and 2 were non-nodular A2.

This means at least 63 (34 "A1" and 29 "A2 other") of 78 cases (81%) had no nodules detected by ultrasound in the previous round which could have developed into cancer. Akira Ohtsuru, the head of the TUE essentially reiterated that they were "newly detected" rather than "newly formed." (See this post for details of Ohtsuru's previous claim). 

An issue of the female to male ratio
The female to male ratio of cancer cases warrants a special attention. For thyroid cancer, the female to male ratio is nearly 1:1 in the very young, but it is known to increase with age and decrease with radiation exposure. (See below Slide 2 in this post for more information). In the second round, the overall female to male ratio is 1.22:1, but the FY2015 municipalities have consistently shown a higher number of males than females with the most recent female to male ratio of 1:1.38. For the third round, the female to male ratio started out with 1:1, and now 1:1.33.

What Ohtsuru said about the the female to male ratio is essentially the same as his statement at the previous two meetings, justifying the low female to male ratios observed in this population without concrete scientific evidence. (Refer to this post or the fact sheet for details).

Reporting results by regions, not municipalities
From the third round onward, confirmatory examination results are no longer available by individual municipalities as before. Rather, the results are reported by four regions:
1) 13 municipalities in the evacuation zone (some municipalities only partially evacuated)
2) Nakadori (central region)
3) Hamadori (eastern, coastal region)
4) Aizu (western region)

Reasoning behind this, according to FMU, is to protect privacy and deter discrimination against those from smaller municipalities diagnosed with thyroid cancer. Ohtsuru backed up the new reporting format by explaining how medical data based on the national insurance claim are protected by not disclosing the number of cases in municipalities with population fewer than 2,000, as per the guidelines established by the Ministry of Health, Labour and Welfare. This regional reporting of cancer cases will essentially make comparisons between the second round and the third round data impossible.

New study to document unreported cases of thyroid cancer
It was announced that a new "research" project was to be launched to investigate how many cases of thyroid cancer were not included in the official count (see the document in Japanese here). Currently awaiting approval from the Ethics Board of FMU, this research project is to be conducted through September 30, 2019 by Susumu Yokoya, Director of Thyroid and Endocrine Center at Fukushima Global Medical Science Center, Fukushima Medical University.

The issue of unreported cancer cases came to light back in March 2017, when it was discovered that thyroid cancer diagnosed in a boy (age 4 at exposure) during follow-up medical visits was not included in the official count. The boy apparently had surgery at FMU, but his case wasn't in the official count because he was under regular medical care using national health insurance.

The new research project apparently will go through medical records at FMU to find cases that had positive fine-needle aspiration cytology results and/or surgery. For each case, an inquiry will be made with the Radiation Medical Science Center to see if it's been included in the official count, in order to tally up unreported cases of thyroid cancer.

Just why it would take UP TO SEPTEMBER 2019 to conduct this seemingly simple investigation was the question on everyone's mind. Also, this project would identify unreported cases diagnosed at FMU only.

International Expert Committee
Incidentally, this meeting coincided with the first day of the First Expert Meeting of Thyroid Monitoring after Nuclear Accidents (TM-NUC) by IARC, held on October 23-25, 2017 in Lyon, France. TM-NUC is the final product of a call for a new third-party committee" by Chairman Hoshi at the 26th Oversight Committee held on December 27, 2016. This call for a new "international, third-party, neutral, scientific, up-to-date and evidence-based" expert committee appears to have originated from the October 31, 2016 recommendations (PDF link here) by the 5th International Expert Symposium on Radiation and Health held on September 26-27, 2016. 

Details on circumstances regarding how TM-NUC came about are described in this post.


Below is the summary of the basic information from each round of screening.

First Round Screening (October 2011 - April 2015)
(This is the updated final results as of March 31, 2017).
The number of confirmed and suspected cancer cases remains the same, but some information has been corrected for duplicates.

Total number targeted: 367,649
Number of participants in primary examination: 300,473
Number with confirmed results: 300,473
  • A1   154,605 (51.5%) (no nodules or cysts found)
  • A2   143,574 (47.8%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
  • B        2,293   (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 confirmatory (secondary) examination: 2,293
Number of participants in confirmatory (secondary) examination: 2,130
Number with confirmed results : 2,090
Number of fine-needle aspiration cytology (FNAC): 547
Number of cases suspicious or confirmed of malignancy: 116 (including one case of benign nodules)
Number with confirmed tissue diagnosis after surgery: 102
  • 1 benign nodule
  • 100 papillary thyroid cancer
  • 1 poorly differentiated cancer
Second Round Screening (April 2014 - March 2016) (see report here)
Total number targeted: 381,256
Number of participants in primary examination: 270,516
Number with confirmed results: 270,515
  • A1   108,710 (40.2%) (no nodules or cysts found)
  • A2   159,578 (59.0%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
  • B        2,227  (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 confirmatory (secondary) examination: 2,227
Number of participants in confirmatory (secondary) examination: 1,844
Number with confirmed results : 1,788
Number of fine-needle aspiration cytology (FNAC): 205
Number of cases suspicious or confirmed of malignancy: 71
Number with confirmed tissue diagnosis after surgery: 50
  • 49 papillary thyroid cancer
  • 1 "other" thyroid cancer
Third Round Screening (May 2016 - March 2018) (see report here)
Total number targeted: 336,631
Number of participants in primary examination: 138,422
Number with confirmed results: 123,857
  • A1   43,388 (35.0%) (no nodules or cysts found)
  • A2   79.715 (64.4%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
  • B          754  (0.6%) (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 confirmatory (secondary) examination: 754
Number of participants in confirmatory (secondary) examination: 438
Number with confirmed results : 367
Number of fine-needle aspiration cytology (FNAC): 18
Number of cases suspicious or confirmed of malignancy: 7
Number with confirmed tissue diagnosis after surgery: 3
  • 3 papillary thyroid cancer

Table 6. Cytology results (as of June 30, 2017) 
(including information from Appendix 6: Number of surgeries among cases with malignancy or suspicion of malignancy)

Second Round Screening

Third Round Screening

Age distribution (age at the time of the March 2011 accident)

No comments:

Fukushima Thyroid Examination October 2021: 221 Surgically Confirmed as Thyroid Cancer Among 266 Cytology Suspected Cases

Overview      On October 15, 2021,  t he 43rd session of the Oversight Committee  for the Fukushima Health Management Survey (FHMS) convened...