Fukushima Thyroid Examination October 2019: 174 Surgically Confirmed as Thyroid Cancer Among 231 Cytology Suspected Cases


Highlights 
  • The third round: 5 cases newly diagnosed as suspicious or malignant, and 1 new case surgically confirmed.
  • The fourth round: 8 cases diagnosed as suspicious or malignant, and no surgical case. Age/sex distribution reported for the first time.
  • Total number of suspected/confirmed thyroid cancer is now 230 excluding a single case of benign tumor: 115 in the first round, 71 in the second round, 29 in the third round, 13 in the fourth round, and 2 in Age 25 Milestone Screening.
  • Total number of surgically confirmed thyroid cancer cases has increased by 1 to 174 (101 in the first round, 52 in the second round,19 in the third round, 1 in the fourth round, and 1 in Age 25 Milestone Screening).
  • This is the first session of the 2019-2021 term for new and returning committee members. 

The latest overall results including "unreported" cases
(See this post for details of the "unreported" cases.)

Overview
     On October 7, 2019, the 36th session of the Oversight Committee for the Fukushima Health Management Survey (FHMS) convened in Fukushima City, Fukushima Prefecture. This was the first session of the 5th term, and the agenda centered on the Thyroid Ultrasound Examination (TUE) in order to familiarize the new members with the scheme and current status of the TUE. The Interim Summary for the second-round results was presented along with a summary of discussion from the 35th session.
    The latest results of the third and fourth rounds of the Thyroid Ultrasound Examination (TUE) (as of June 30, 2019) were also released. Official English translation, ordinarily available on the website of Office for International Cooperation at the Radiation Medical Science Center for the Fukushima Health Management Survey, has not been released since the 33rd session on December 27, 2018. According to the most recent entry in Announcements, this translation was posted online on April 5, 2019, over 3 months after the 33rd session was held. This is a lot longer than the previous turnaround time of 3-4 weeks up to the 31st session. Now that the official translation is 3 sessions behind, it remains to be seen whether FMU is even going to continue to provide it.

Summary on the current status of the TUE
     A six-page summary of the first through fourth rounds as well as the Age 25 Milestone Screening, "The Status of the Thyroid Ultrasound Examination," lists key findings from the primary and confirmatory examinations as well as the surgical information. This summary is not translated into English officially, but here's an unofficial translation which hopefully helps make up for the unavailability of the entire results in English. 


Key points from the Oversight Committee

New and returning member list
   The 2019-2021 term (the fifth term) of the Oversight Committee consists of 18 members including 6 new faces, with an addition of one more member than the previous term. The new roster is available here (only in Japanese).
   No immediate plan has been announced to convene the third term of the Thyroid Examination Evaluation Subcommittee whose purpose to analyze the third-round results. But the new roster has already been released. 
   Notably, Toru Takano of Osaka University, a controversial figure who held dual positions in the Oversight Committee and the Thyroid Examination Evaluation Subcommittee during the last term, is out the door.

 Oversight Committee members (August 1, 2019 to July 31, 2021) 



 ＊＊＊ Special note ＊＊＊
   Hideo Tatsuzaki warrants a special mention. He occupies the 18th position on the roster which was newly added this term. An addition of this position was never brought up or discussed publicly during the last term and appears to be at the discretion of an unknown party, perhaps the prefectural government. In view of the fact that his immediate superior at QST is Shunichi Yamashita, who is Director General at the Center for Advanced Radiation Emergency Medicine, Tatsuzaki could effectively be considered Yamashita's surrogate. 
   A Tokyo Shimbun article published in the morning edition on January 28, 2019 states that Tatsuzaki was a leader of the medical team at the Offsite Center, an emergency response measures base facility established in Fukushima Prefecture during the immediate post-accidental period. 
   Also, according to the self-declaration form submitted to the Technical Committee on Nuclear Power Safety Management in Niigata Prefecture, Tatsuzaki was affiliated as a radiation oncologist with IAEA from 1997 to 2001 as First Officer in the section of Applied Radiation Biology and Radiotherapy, Department of Human Health, IAEA. Tatsuzaki was also a member of the Ministry of Foreign Affairs domestic committee for IAEA/RCA lead country in the field of health and medicine in FY2018-2019. (RCA stands for Regional Cooperative Agreement for Research, Development and Training Related to Nuclear Science and Technology for Asia and the Pacific.)
   His ties with Yamashita and IAEA could put Tatsuzaki in a position to ascertain "dismissal" of any radiation effects potentially observable in the third and fourth rounds, complementing FMU's ongoing efforts to withhold data needed for meaningful and transparent analysis. 

    
Thyroid Examination Evaluation Subcommittee (TUE Subcommittee) members (August 1, 2019 to July 31, 2021)

  • Shuji Asahi, M.D. (new member replacing Hirofumi Ami; thyroid and breast surgeon), Chief, Department of Endocrine and Breast Surgery, Aizu Chuo Hospital (recommended by the Fukushima Hospital Association)
  • Tsuneo Imai, M.D. (new member replacing Akira Yoshida; endocrine and breast surgeon), Director, Higashinagoya National Hospital (recommended by the Japan Association of Endocrine Surgery)
  • Kota Katanoda, Ph.D. (returning member; statistician), Chief, Division of Cancer Statistics Integration, Center for Cancer Control and Information Services, National Cancer Center
  • Tetsuo Kondo, M.D., Ph.D. (new member replacing Ryohei Kato; pathologist), Associate Professor, Department of Human Pathology, Yamanashi University
  • Gen Suzuki, M.D., Ph.D. (returning member; former chairperson of the TUE Subcommittee; radiation researcher), Director, International University of Health and Welfare Clinic (recommended by the Japanese Radiation Research Center)
  • Tomotaka Sobue, M.D., M.P.H. (returning member; cancer epidemiologist), Professor, Department of Social and Environmental Medicine, Division of Environmental Medicine and Population Sciences, Graduate School of Medicine, Osaka University (recommended by the Japan Epidemiological Association)
  • Kanshi Minamitani, M.D., Ph.D. (returning member; pediatric endocrinologist), Clinical Professor, Department of Pediatrics, Teikyo University Medical Center (recommended by the Japanese Society for Pediatric Endocrinology)
  • Tsukasa Murakami, M.D. (new member replacing Toru Takano; endocrinologist), Director, Noguchi Thyroid Clinic and Hospital Foundation (recommended by the Japan Thyroid Association)


The third round
   The third-round results between April 1, 2019 and June 30, 2019 show that the primary examination participation rate remained at 64.7% with an additional 177 undergoing the examination. Nine more participants, assessed "B," became eligible for the confirmatory examination. 
   Nine participants (not necessarily the same nine previously mentioned) underwent the confirmatory examination and five that newly underwent FNAC were all diagnosed with suspected thyroid cancer. This makes "29" the total number of suspected thyroid cancer cases in the third round.
   The 5 new suspected thyroid cancer cases consist of 3 males (ages-at-exposure: 6, 6, and 8) and 2 females (ages-at-exposure: 10 and 11), with 2 from Hamadori and 3 from Aizu. The second-round results for these five cases were 1 case with A1, 2 cases with A2 cyst, and 2 cases with B, meaning 3 of 5 had no previous sign of cancerous lesion 2 years ago.
   There was only one new surgical case from the third round, with the total of 19 surgically confirmed thyroid cancer cases. Because the Japanese summer break for elementary through high schools is usually from late July through August (longer for colleges), the next set of data as of September 30, 2019 (to be released in late December) is likely to include more cytology and surgery results.

The fourth round
   The fourth round, scheduled from April 1, 2018 through March 31, 2020, is actively ongoing. The current participation rate for the primary examination of 40.1%, lower than the previous rounds (81.7% for the first round, 71.0% for the second round, and 64.7% for the third round), is expected to increase especially with the progress of the school examination in the FY 2019 municipalities. Nonetheless, just how high it will get remains to be seen.
  Eighty-one participants newly underwent the confirmatory examination which raised a participation rate to 59.8%. Twelve participants, all from the FY2018 municipalities, newly underwent FNAC, and 8 of them were diagnosed with suspected thyroid cancer, making "13" the total number of suspected thyroid cancer cases in the fourth round.
   The 8 suspected thyroid cancer cases are all from Nakadori, consisting of 4 males and 4 females. Because this is the first time that the age and sex distribution graph for the fourth round was released, it is not possible to specify ages-at-exposure for the 8 new suspected thyroid cancer cases. However, it is possible to identify age and sex for the entire 13 suspected cancer cases in the fourth round which include 6 males (ages-at-exposure: 5, 5, 7, 7, 12, and 12) and 7 females (ages-at-exposure: 4, 6, 8, 9, 10, 10, and 10). 
   As can be seen, there are more patients who were aged 5 years or younger at exposure. There might be more thyroid cancer cases detected in those who were aged 5 years or younger from now on, but declining participation rates with successive screening rounds are likely to dampen the reliability of the data. Moreover, once patients are placed on the clinical follow-up track, which can happen when potential thyroid cancer risk is identified but no immediate diagnosis is made for various reasons directly during the confirmatory examination, they essentially disappear into a "black box": any cancer cases diagnosed in the black box become "unreported cases" which are not included in the official tally. Although some of the "unreported" cases have been revealed as described in this post, publicly available data is far from a true and complete picture of the situation.
   In addition, there is no way to identify which cancer occurred as a result of radiation exposure, but their previous results from the earlier rounds might give some hint. The third-round results for the 8 newly diagnosed suspected cases were 2 cases with A1, 2 cases with A2 cyst, 2 cases with A2 nodule, and 2 cases with B. However, their results in the first and second rounds are not publicly available. (No doubt that FMU has such information.)
   There was no new surgical case for the fourth round at this time. As mentioned in the previous section, the next set of data as of September 30, 2019, to be released in late December, will probably include more surgeries because the patients might defer surgery until the summer break so as not to interfere with school work.

Results from the previous screening 
     Below is information on previous assessments of the suspected/confirmed thyroid cancer cases. In the second round, 33 of 71 cases were assessed as "A1" meaning there were no ultrasound findings. Thirty-two were assessed as "A2" with ultrasound findings of nodules ≤ 5.0 mm and/or cysts ≤ 20.0 mm, 5 were assessed as "B" with nodules ≥ 5.1 mm and/or cysts ≥ 20.1 mm. Of 32 cases with A2, 25 cases had cysts. Having previous assessments of "A1" or "A2 cysts" means there was no precancerous lesion during the prior TUE, i.e., cancer supposedly appeared since the prior TUE. (Note: FMU claims the cancerous lesions were simply "invisible" during the prior TUE.)
  • Second round (71 cases): 33 cases with A1, 32 cases with A2 (7 nodules and 25 cysts), 5 cases with B, 1 case unexamined
  • Third round (29 cases):  6 cases with A1, 13 cases with A2 (3 nodules and 10 cysts), 7  cases with B, 3 cases unexamined
  • Fourth round (13 cases): 2 cases with A1, 8 cases with A2 (6 nodules and 2 cysts), 3 cases with B


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Fukushima Thyroid Examination July 2019: 173 Surgically Confirmed as Thyroid Cancer Among 218 Cytology Suspected Cases

*See this post for various issues surrounding Fukushima's Thyroid Ultrasound Examination (TUE) data.
**Made corrections and clarifications in description of "FY" in the Age 25 Milestone Screening section. (September 28, 2019)
***Table for The latest overall results including "unreported" cases was replaced with a corrected version showing that Age 25 Milestone Examination was conducted in FY2017-8, not FY2016 as stated in the original version. (September 28, 2019)
****Status of the Thyroid Ultrasound Examination PDF was updated to reflect the correct number of surgical cases (18, not 15 as previously shown) for the third round. (October 9, 2019)

Highlights 
  • The third round: 3 cases newly diagnosed as suspicious or malignant, and 3 new cases surgically confirmed.
  • The fourth round: 3 cases diagnosed as suspicious or malignant, and 1 new case surgically confirmed.
  • Total number of suspected/confirmed thyroid cancer is now 217 excluding a single case of benign tumor: 115 in the first round, 71 in the second round, 24 in the third round, 5 in the fourth round, and 2 in Age 25 Milestone Screening.
  • Total number of surgically confirmed thyroid cancer cases has increased by 5 to 173 (101 in the first round, 52 in the second round,18 in the third round, 1 in the fourth round, and 1 in Age 25 Milestone Screening).
  • This is the last session of the 2017-2019 term. 

 The latest overall results including "unreported" cases

(See this post for details of the "unreported" cases.)

Overview
     On July 8, 2019, the 35th Oversight Committee for Fukushima Health Management Survey (FHMS) convened in Fukushima City, Fukushima Prefecture. Agenda included various fiscal reports from FY2018 (April 1, 2018 to March 31, 2019).
     Among other information, the Oversight Committee released the latest results (as of March 31, 2019) of the third and fourth rounds of the Thyroid Ultrasound Examination (TUE). Also released were the biannual results of Age 25 Milestone Screening. Official English translation should eventually be available here. (Note: English translation for the December 27, 2018 meeting was posted online on April 5, 2019, over 3 months later.)

 Summary on the current status of the TUE
     A five-page summary of the first through fourth rounds as well as the Age 25 Milestone Screening, "The Status of the Thyroid Ultrasound Examination," lists key findings from the primary and confirmatory examinations as well as the surgical information. This summary is not translated into English officially, but here's an unofficial translation. (Note: This translation has an additional pieces of information—the average age and tumor diameter for the FNAC results of the fourth round—which were not included in the original Japanese version.)

Key points from the Oversight Committee

 The interim report on the second round results
     The interim report, finalized at the 13th Thyroid Examination Assessment Subcommittee held on June 3, 2019, was presented and discussed. (See the previous post for unofficial translation of the draft version.) The final version varies very little from the draft version, with an addition of "and prospective" to the second to the last sentence as follows:
Further, in the future, estimated thyroid exposure doses should be used in case control and prospective studies with confounding factors adjusted, in order to evaluate an association between doses and thyroid cancer incidence rates.
     Discussion mainly revolved around the decisive nature of the phrase, "Thus, at this time, no association is seen between thyroid cancer detected in the second round and radiation exposure," which was considered too premature by multiple committee members. Their opinions were complied in a supplementary document, but not reflected in the final version of the interim report.

Age 25 Milestone Screening
     The results released at this time include those born in FY1993 (April 1993 to March 1992) (April 2, 1993 to April 1, 1994) in addition to the previously reported results from those born in FY1992 (April 2, 1992 to April 1, 1993). (Note: "FY" here is "academic FY" that applies to students in a particular school grade: students born during a particular academic FY belong to the same grade.)

      The participation rate remains low at 7.1%. Many might be either forgoing the TUE altogether or undergoing it at their local medical facilities rather than returning to Fukushima. Fukushima Medical University (FMU) does have affiliation agreements with 120 non-Fukushima medical facilities nationwide (see the list in Japanese), but these young adults with busy schedule might choose more convenient locations outside the list.

      Officials intend to rely on cancer registry data to supplement data, but it may not be easy or adequate as described below.
Cancer registry in Japan 
The 2016 National Cancer Act mandates collection of cancer data nationwide. Hospitals (≥ 20 beds) are required to report cancer data, but clinics (≤ 19 beds) need to be voluntarily "designated" by prefectures in order to report cancer data. This loophole implies that the cancer registry data might not to be as exhaustive as it should be.  (See the National Cancer Center website for more information in English.) It is also conceivable that some "clinics" could function as a shelter for unreported cancer cases.
Results from the previous screening 
     Below is information on previous assessments of the suspected/confirmed thyroid cancer cases. In the second round, 33 of 71 cases were assessed as "A1" meaning there were no ultrasound findings. Thirty-two were assessed as "A2" with ultrasound findings of nodules ≤ 5.0 mm and/or cysts ≤ 20.0 mm, 5 were assessed as "B" with nodules ≥ 5.1 mm and/or cysts ≥ 20.1 mm. Of 32 with A2, 25 had cysts. Having previous assessments of "A1" or "A2 cysts" means there was no precancerous lesion during the prior TUE, i.e., cancer supposedly appeared since the prior TUE. (Note: FMU claims the cancerous lesions were simply "invisible" during the prior TUE.)

  • Second round (71 cases): 33 with A1, 32 with A2 (7 nodules and 25 cysts), 5 with B, 1 unexamined
  • Third round (24 cases):  5 with A1, 11 with A2 (3 nodules and 8 cysts), 5 with B, 2 3* unexamined
  • Fourth round (5 cases): 4 with A2 (4 cysts), 1 with B
*Corrected on November 12, 2019. 


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How the "Conclusion" Transpired on Thyroid Cancer in the Second Round in Fukushima

Note: In translation of the official documents, "detection rate(s)" is used instead of "incidence rate" or "prevalence rate" in accordance with the original Japanese terminology.

Leaked "conclusion"

     On May 31, 2019, a Kyodo News article titled, "A Link Denied Between the Nuclear Power Plant Accident and Cancer in the Full-Scale Thyroid Screening in Children," appeared on the websites of Tokyo Shimbun and Okinawa Times. Below is an unofficial translation.
     An interview with an official on May 31 revealed that the expert subcommittee summarized an interim report reporting no link between cancer detected during the second round of the Thyroid Ultrasound Examination (TUE) and radiation exposure. The TUE covers all children in Fukushima Prefecture who were aged ≤ 18 years when the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident occurred, and the second round screening was conducted during FY 2014–2015. The reason for reporting no link is because there was no correlation showing an increased cancer rate at a higher exposure dose.
     As opposed to the first round that was intended to collect the baseline data, the second round is considered "Full-Scale Screening" which investigates effects of the accident on cancer. Now that opinions on the second round have been summarized for the first time, the future of the TUE might be impacted.

     This report came as a surprise to many of us who have been following the development of the Oversight Committee for the Fukushima Health Management Survey (FHMS) and one of its subcommittees, the Thyroid Examination Evaluation Subcommittee (herein, the TUE Subcommittee), for a simple reason that the analyses and deliberations conducted so far did not seem adequate to draw such a hasty conclusion. Discussions at the Subcommittee sessions have mostly been dominated by benefits and harm of the TUE itself, leading to an ongoing revision of the informed consent form. 
     It is true that an "interim report" was expected, as customary with any government committee, with the two-year term for the current TUE Subcommittee roster coming to a close as of the 13th TUE Subcommittee meeting held on June 3, 2019. What was not expected was that it would be such a hasty conclusion with a decisive tone.

 "Draft" summary

     Chairperson Gen Suzuki started the meeting off complaining that the "scoop" headlines would take on a life of its own without conveying the process of discussion that led to the conclusion. The actual "interim report" released at the 13th Subcommittee meeting turned out to be only a "draft summary," and the conclusion was considered provisional.
     Accuracy of media reports released after the meeting seemed to depend on how well the writers have been informed of this complicated issue. Unfortunately, the only English article by Mainichi, "Thyroid cancer diagnoses in Fukushima youth not linked to nuke disaster: panel" did not accurately convey the original Japanese title "Thyroid cancer in Fukushima youth and radiation exposure 'not linked at this time': subcommittee" that emphasized the temporary nature of the conclusion. (Also the phrase in the Mainichi English article, "there is no data on those who have yet to be examined," is mistranslation of the original Japanese text that refers to lack of data on those who were examined outside the TUE system, explained as missing data in the previous post.

      Granted, the draft summary presented is only a draft. But the conclusion seems too decisive despite "provisional," considering the quality of analyses and discussions conducted so far. Some of the subcommittee members were not happy about the decisive tone of the draft summary, making suggestions to tone it down.
     In honor of Suzuki's wish to "convey the process of discussion that led to the conclusion," relevant documents have been translated into English. Translation of the draft summary is posted here, and translation of FMU's analyses used to draw the "provisional conclusion" will follow in the latter part of this post. 

      First, some background information is offered to characterize this TUE Subcommittee and "convey the process of discussion."

 Analyses dominated by FMU
    
    When the TUE Subcommittee was reconvened after nearly a three-year hiatus in order to analyze the second-round data, there was an expectation that the analysis would be conducted by the subcommittee members which included experts in thyroid surgery, pediatrics, pathology, cancer statistics, epidemiology, and thyroid cancer research. However, the Subcommittee has been able to do little more than listening to Fukushima Medical University (FMU) officials presenting their own analyses of the data, mostly consisting of proportions without actual numerical results. 
    The subcommittee members have had to repeatedly ask for the actual data to no avail. When FMU officials said that after confounding factors were adjusted some results of analyses yielded a very small number, 1 or 2 cases, from very small municipalities that might make them identifiable, the members even offered, more than once, to hold a closed session to secure privacy of data. When FMU officials shared their hesitation to share raw data because it should not be looked at without removing confounding factors, chairperson Suzuki suggested that FMU share data at least with experts in statistics and epidemiology, if not the entire subcommittee, to help them sort through issues. 
     None of the advices or suggestions were taken up by FMU. Instead, they would submit analyses after analyses with their own interpretations. The subcommittee members would listen, ask question, offer some opinions and advises. Never once were the subcommittee members involved in analyzing the actual data simply because of the lack of opportunity. 

     (Note: During an informal interview immediately after the 13th Subcommittee press conference, chairperson Suzuki allegedly said that FMU withheld the actual raw data so as not to let a "certain magazine" publish its own analysis which would then take on a life of its own. Most certainly that magazine is Kagaku by Iwanami Publishers.)

 Other futile discussions
     
     For some reason, when the TUE Subcommittee resumed, its members were still debating benefits and harm of the TUE itself even when the third round was fully under way. Recognition of the TUE as typical cancer screening, rather than health monitoring as described in the previous post, set the tone for the never-ending debate throughout the term of this TUE Subcommittee. The debate even intensified after the IARC expert group TM-NUC (Thyroid Monitoring after Nuclear Accident) released its report, recommending against systematic thyroid screening for fear of overdiagnosis. (See this 2017 post or previous post for more on TM-NUC.) 
     Further, Toru Takano, a thyroid cancer researcher from Osaka University and the only subcommittee member doubly appointed to the Oversight Committee, kept insisting that the TUE administered in school-settings (in elementary and junior high schools) constituted an ethical and human rights violation because students were "forced" into it. (The truth is that the school-based TUE, approved by FMU's ethics committee, had been requested by municipal education commissions to prevent missed school days and extra load on families from taking children to a specified TUE location. Only students with signed consent forms are examined.) 
     According to Takano's own hypothesis of fetal cell carcinogenesis, all children have "self-limiting thyroid cancer." Hence all thyroid cancer cases detected in Fukushima comprise overdiagnosis, so the TUE should immediately be stopped and replaced by palpation of the neck. Why Japan Thyroid Association appointed Takano to the double positions is unclear. If the intention was to create disturbance and muddle the debate, their choice certainly nailed it.

Disappearing regional differences

      As described in the previous post, the TUE data has numerous transparency and reliability issues. Still, some meaningful analysis on the official data could be of use. 
     The final report of the second round has never been translated into English because it was first presented to the 8th TUE Subcommittee as Document 2-1. (Documents from subcommittee are never officially translated.) Included in the final report is Table 11 for a regional analysis which, unlike in the first round (see Table 9), appears to show regional differences in detection rates of thyroid cancer in the second round (shown in the bottom rows). (See the comparison between Tables 11 and 9 in this post.)
     Also presented at the 8th TUE Subcommittee meeting as Document 2-3 was another set of the regional analysis adjusted with screening interval, the length of time between primary examinations of the first and second rounds. This analysis only includes 246,687 subjects who participated in both of the first and second rounds, eliminating 23,829 or nearly 9% of 270,516 participants. 
     Table 11 and the version adjusted for screening interval is shown below.

 The second-round results by region: original Table 11 and adjusted for screening interval by on Scribd

   
    Other than this adjustment for screening interval, FMU has compared the first- and second-round data (see Document 2 from the 10th Subcommittee) and done just about everything seemingly possible to "adjust" detection rates of confirmed or suspected cancer for various factors which can affect the second-round data (see Document 1 from the 11th Subcommittee). Excerpts fro these 2 documents were presented as Document 1-1 at the 13th Subcommittee meeting.

 Dose-response analysis with UNSCEAR doses

      Their effort culminated in a dose-response analysis using absorbed doses to the thyroid by municipality estimated by UNSCEAR. Presented as Document 1-2 at the 12th Subcommittee meeting on February 22, 2019, it claimed no dose-response in confirmed or suspected cancer cases from the second round. Of course, the best doses to be used are individual thyroid doses, but only 1080 children from 3 municipalities had their thyroids directly measured (and these measurements are likely underestimated). UNSCEAR estimated doses by municipality were considered by chairperson Suzuki the only "authorized" doses available at present to be used in a dose-response analysis, despite reservations about its use as expressed by experts from National Cancer Center Japan.
     This dose-response analysis has been severely criticized by Junichiro Makino, an astromist/physicist at Kobe University, for questionable methods in a Japanese science journal Kagaku (only available in Japanese). Makino has previously pointed out in his 2015 book "Assessment of radiation exposure and scientific methods" that thyroid absorption doses estimated by UNSCEAR have a significant amount of uncertainties because they are essentially based on deposition of radioactive cesium 134/137. 
     It is not radioactive cesium but radioactive iodine that affects the thyroid gland. However, due to a very short half-life (8 days) of radioactive iodine 131 and even shorter half-life (2.3 hours) of iodine 132 existing in equilibrium with tellurium 132 (half-life 3.2 days), it is extremely difficult to conduct actual measurements of radiological contamination due to short-lived iodine isotopes. Thus UNSCEAR-estimated thyroid absorption doses were calculated from radioactive cesium levels based on a theoretically-derived cesium-to-iodine ratio which in reality may not remain the same under different circumstances.
     In short, results from the dose-response analysis using UNSCEAR estimated doses would not be considered very reliable due to a significant amount of inherent uncertainties. 

 Underestimation due to an error 

     At the June 3, 2019 TUE Subcommittee meeting, FMU admitted that an error made while entering data in analytical program of statistical software had produced odds ratios which were smaller than actual values. A correction (Document 1-3, translation shown below) was issued that showed bigger odds ratios and wider 95% confidence intervals. Insisting that the error does not change the results of significant testing, FMU upholds their conclusion of no dose-response. 
     As to preventing future errors, FMU formed an investigative committee to look into the matter and decided to establish a system where two individuals would conduct the same analysis and compare results. With their competency in question, a better option might be a third-party analysis and oversight.

 New analysis 

    As if to back up their "no dose-response" claim, FMU also released further odds ratio analyses (Document 1-2, translation shown below) with an adjustment of various factors. The "new" analysis released at the same time as the draft summary was bizarre. 
     The subcommittee members appeared literally at a loss. In fact, some stated that it was difficult to interpret the results without seeing the number of cases in each dose group. Others seemed to be having difficulty digesting FMU's own analyses and interpretation in a short time. 
     In particular, some of the graphs actually show a negative trend, with odds ratios falling below 1. Testuya Ohira, an FMU official, explains, "a negative trend seen is an unlikely item in general, so for now we are calling it no dose-response."

⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨⬨

     At the 12th Subcommittee meeting in February 2019, it was becoming clear that the TUE Subcommittee was running out of time to make a proper assessment before the two-year term was up, but in our naivety, some of us anticipated that discussion might be carried onto the next term without drawing any definitive conclusion. 
     However, what actually took place at the very last meeting of the current term was beyond words: Based on FMU's analysis criticized for lack of transparency or comprehensibility from start to finish, chairperson Suzuki put together a draft summary with a provisional conclusion of no radiation effects for thyroid cancer detected in the second round. 
     When asked to "grade" the conclusion at the press conference, Tomotaka Sobue, a cancer epidemiologist, gave 60 out of 100, and Kota Katanoda, a cancer statistician, gave 50. They both pointed to 2 things that account for the tentative nature of the conclusion, 1) lack of individual doses and 2) missing data on cancer cases diagnosed during the clinical follow-up or outside the TUE.  
     Suzuki says the provisional conclusion is to be treated with caution because the second-round data will eventually be re-analyzed. Unfortunately, once it hits a headline, the provisional conclusion is likely to skip whatever nuance is intended and take on a life of its own. 

 Translation of the FMU analyses

      Below is the translation of 3 documents presented to the 13th TUE Subcommittee on June 3, 2019. Showing analyses by FMU, these documents comprise the basis for the "provisional conclusion" that denies radiation effects for the second round of the TUE. 



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English Translation of a Draft Summary on Fukushima's Thyroid Cancer Found in the Second-Round Screening

⁂ This is an unofficial English translation of the draft version of the official summary on the second-round results.
⁂ Update on November 10, 2019: The final version submitted to the 35th meeting of the Oversight Committee on July 8, 2019 had an addition of "and prospective" in the second to the last sentence as shown below.
   Further, in the future, estimated thyroid exposure doses should be used in case control and prospective studies with confounding factors adjusted, in order to evaluate an association between doses and thyroid cancer incidence rates.
＊＊＊＊＊＊＊＊＊     
     On June 3, 2019, the 13th Thyroid Examination Evaluation Subcommittee (herein, the TUE Subcommittee) was held, marking the end of a two-year term for the members. As it is customary for committees to produce a report at the end of the term, a draft version of the "interim report" was submitted by Gen Suzuki, chair to the TUE Subcommittee, concluding, "at this time, no association is seen between thyroid cancer detected in the second round and radiation exposure."
     The conclusion, albeit provisional, came as a surprise to many, because it did not seem like the TUE Subcommittee had spent enough time analyzing the second-round data. On the contrary, most of discussions have revolved around the topic of benefits and harm of the TUE itself.
     When this "provisional" conclusion became known to English speakers via a online newspaper article on the Mainichi website, confusion ensued. English translation of the "interim report" is offered below so everyone can see the "basis" for the conclusion by the TUE Subcommittee. Translation of some of the analyses mentioned is to be posted separately.

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Note: This is a draft version. The final version is expected to have slightly different wording. (See the update at top.)


   A summary of the subcommittee regarding the results of the Full-Scale Screening of the Thyroid Ultrasound Examination (the second round)

June 3, 2019

Thyroid Ultrasound Examination Evaluation Subcommittee by the
Oversight Committee for Fukushima Health Management Survey

     The Thyroid Ultrasound Examination (herein, TUE) Evaluation Subcommittee by the Oversight Committee for Fukushima Health Management Survey (herein, the Subcommittee) released an “Interim Summary on the TUE” (herein, the Interim Summary) in March 2015 to report on the results of the Initial Screening of the TUE (the first round) conducted from FY 2011 to FY 2013. The Interim Summary concluded that the results of the first round “were unlikely to be the effects of radiation.”
     At the 26th Oversight Committee for Fukushima Health Management Survey (herein, the Oversight Committee) held on February 20, 2017, a proposal was made to convene the Subcommittee in order to summarize and evaluate the results of the Full-Scale Screening of the TUE (the second round, FY 2014-2015). In response to this proposal, the 7th Subcommittee was convened in conjunction with the 27th Oversight Committee on June 5, 2017, followed by the 8th Subcommittee held with a new set of members on November 30, 2017. The Subcommittee engaged in repeated deliberations over a total of 7 sessions, up to the 13th Subcommittee held on June 3, 2019.
     Based on the contents of the deliberations, the Subcommittee summarized below the results of the second round, opinions of the Subcommittee on the results, and issues for future consideration.

1    Results of the Full-Scale Screening of the TUE (the second round)

     The second round that began in April 2014 covered approximately 380,000 Fukushima residents, adding subjects born between April 2, 2011 and April 1, 2012 to the first-round subjects born between April 2, 1992 and April 1, 2011. About 270,000 have participated as of June 30, 2017 (participation rates of 71% overall, 86.4% in ages ≤ 17, 25.7% in ages ≥ 18), and 2227 (0.8%) were assessed the B test results requiring a confirmatory examination and no one had the C test result (note: requiring an immediate confirmatory examination). After undergoing fine-needle aspiration cytology (FNAC) during the confirmatory examination, 71 were diagnosed with confirmed or suspected malignancy (26.2/100,000; 32 males and 39 females; average age 16.9 ± 3.2 years, age range 9-23 years; average age at the time of the accident 12.6 ± 3.2 years, age range 5-18; average tumor diameter 11.1 ± 5.6 mm). (Note: 52 underwent surgery, revealing 51 papillary thyroid cancer and 1 other cancer.)
     The detection rate of thyroid cancer during the first round was several orders tens of times multiples of ten higher than prevalence rate/proportion estimated from the Japanese cancer statistics data based on the regional cancer registry. The thyroid cancer detection rate in the second round was somewhat smaller than that in the first round but still several orders multiples of ten higher (than the cancer statistics data).
     Detection rates of confirmed or suspected cancer showed no regional difference in the first round. In the second round, a simple comparison without adjusting for sex and age showed the highest detection rate in the 13 evacuated municipalities, followed by Nakadori, Hamadori, and Aizu.
     However, detection rates of confirmed or suspected cancer are likely influenced by many factors. When some of the factors were considered, the following tendencies were observed.
  • The detection rate of nodules with diameter of 5.1–10 mm was low in the 13 evacuated municipalities in the first round. Also, among subjects with the B test results in the second round, the proportion of the subjects whose first-round results were also B was low in the 13 evacuated municipalities. This suggests that the second-round results are affected by the first-round results.
  • The longer the interval between the first and second rounds, the higher the FNAC rate and the detection rate of confirmed or suspected cancer. The longest average interval was observed in the 13 evacuated municipalities.
  • FNAC rates have declined in successive years even in the first round. The second-round FNAC rate declined in the order of the 13 evacuated municipalities, Nakadori, Hamadori, and Aizu.
  • When FNAC was conducted in the first round, FNAC rates and detection rates of confirmed or suspected cancer tended to be lower in comparison with the subjects who underwent no FNAC in the first round. 

2   Regarding the preliminary analysis on an association between thyroid cancer detection rates in the second round and radiation doses

     The above analysis has shown that detection rates of confirmed or suspected cancer are influenced by many factors other than sex and age at screening, such as screening year, FNAC rates, screening interval since the first round, and whether FNAC was conducted in the first round. Therefore, an evaluation of an association between thyroid cancer detection rates and radiation doses calls for analyses that control these factors.
     For radiation doses, an analysis was tentatively conducted with absorbed doses to the thyroid estimated in different age groups and municipalities by United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR), which incorporate internal exposure.
     The analysis showed no clear association between doses and thyroid cancer detection rates.
          
3   Findings

     Proportions of the B test results in the primary examination, recommended to advance to the confirmatory examination, were larger with an older age at the time of the accident, and detection rates of confirmed or suspected cancer were higher with an older age at the time of the confirmatory examination. This is dissimilar to detection of many more thyroid cancer in a younger age group after the Chernobyl accident. Detection of more cancer with an increasing age is similar to cancer in general.
     The male-to-female ratio is close to 1:1, which is different from what tends to be observed in a clinical setting (about 1:6). It has been reported that the male-to-female ratio tends to be smaller in latent cancer and younger ages. Evaluation of an association between the male-to-female ratio and radiation remains as a future task.
     A simple comparison of detection rates of confirmed or suspected cancer in four regions appears to show differences, but it is influenced by many factors such as screening year and screening interval since the first round. Any analysis needs to take these factors into consideration.
     When factors that can influence detection rates were adjusted as much as possible, analyses of an association between doses and thyroid cancer detection rates, tentatively using the absorbed doses to the thyroid estimated by UNSCEAR by age group and municipality, revealed no consistent relationship between increasing doses and increasing detection rates (dose-effect relationship).
     Thus, at this time, no association is seen between thyroid cancer detected in the second round and radiation exposure.

4   Explanation to residents covered by the TUE

     The Subcommittee has advanced discussion on contents of the explanation to residents covered by the TUE. It is important to continue careful explanation of merits and demerits of the TUE, so their understanding and consent may be gained before the TUE is administered.

5   Viewpoints for future evaluation

     The third round started in FY 2016 and the fourth round in FY 2018, and their results need to be incorporated into further analyses.
     Also, participation rates of the TUE are declining every year. In particular, a participation rate after high school graduation is low with continuing decline expected in the future. Moreover, it is possible that more cancer cases might be discovered outside the TUE conducted as part of the Fukushima Health Management Survey.
     This leads to the use of regional and national cancer registries in order to identify cancer incidence among residents covered by the TUE so an analysis could be conducted.
     Further, in the future, estimated thyroid exposure doses should be used in case control studies with confounding factors adjusted, in order to evaluate an association between doses and thyroid cancer incidence rates.
     These are the viewpoints that should be considered in advancing discussion at the Subcommittee and the Oversight Committee in the future.
      
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