Fukushima Thyroid Examination March 2023: 247 Surgically Confirmed as Thyroid Cancer Among 302 Cytology Suspected Cases



     On March 22, 2023, the 47th session of the Oversight Committee for the Fukushima Health Management Survey (FHMS) convened online and in Fukushima City, releasing a new set of results (data up to September 30, 2022) from the fifth round as well as the biannually reported Age 25 Milestone Screening of the Thyroid Ultrasound Examination (TUE).  It amounts to 3-month worth of data since the previous session held on December 2, 2022 for the fifth round (see previous post) and 6-month worth of data for the Age 25 Milestone Screening since the 45th Oversight Committee session (as reported in this post). 

     In addition, the final results of the 4th round were released at the 20th session of the TUE Assessment Subcommittee (TUE Subcommittee herein) held on March 20, 2023. Unless it is also reported to the next Oversight Committee session, the fourth-round final results might have the same fate as the second-round final results, which was only reported to the TUE Subcommittee, for not having official English translation. However, because the content of the fourth-round final results is identical to the results reported at the 46th session of the Oversight Committee, official translation will eventually appear on the Materials and Minutes of Prefectural Oversight Committee Meetings page (link) of the website of Radiation Medical Science Center of the Fukushima Health Management Survey (RMSC/FHMS). As of today, official English translation is available up to the 42nd session (PDF link)This website also shows an outline of the FHMS and TUE itself.

  • The fourth round: The final report issued.
  • The fifth round: 3 new cases diagnosed as suspicious or malignant, and 9 new surgical cases.
  • Age 25 Milestone Screening: 3 new cases diagnosed as suspicious or malignant and 1 new surgical case.
  • Total number of suspected/confirmed thyroid cancer has increased by 6 to 302116 in the first round (including a single case of benign tumor), 71 in the second round, 31 in the third round, 39 in the fourth round, 26 in the fifth round, and 19 in Age 25 Milestone Screening.
  • Total number of surgically confirmed thyroid cancer cases has increased by 10 to 247 (101 in the first round, 56 in the second round, 29 in the third round, 34 in the fourth round, 16 in the fifth round, and 11 in Age 25 Milestone Screening,

The latest overall results including the "unreported" and cancer registry cases
     Please refer to the the post on May 2021 report regarding the details of "unreported" cases and cancer registry data. (A July 2018 post describes the origin of the first 11"unreported" cases, and their histological diagnoses were obtained from this paper.)

     The official count, as reported above and also in the summary document shown in the next section, is 302 suspected/confirmed and 247 surgically confirmed thyroid cancer cases. With an addition of the most recent numbers for both "unreported" cases (see this post) and "outside" cases discovered in the cancer registry (updated at the 19th session of the TUE Subcommittee), the count increases to 380 cytologically suspected/confirmed and 309 surgically confirmed cancer cases. 
     It should be noted that the actual number of cases is likely more due to lack of any past, present or future exhaustive investigation by Fukushima Medical University (FMU), which is necessary to gather all the cancer cases discovered outside the framework of the FHMS-TUE.

Summary on the current status of the TUE
    A seven-page summary of the first through fifth rounds as well as the Age 25 Milestone Screening, "The Status of the Thyroid Ultrasound Examination Results," lists key findings from the primary and confirmatory examinations as well as the surgical information. 
    Below is an unofficial translation of this summary which is not officially translated.

The first round
     There is no change in data with 116 suspected/confirmed thyroid cancer cases (39 males and 77 females), of which 102 underwent surgery confirming 1 benign nodule and 101 thyroid cancer cases (100 papillary thyroid cancer and 1 poorly-differentiated cancer). 
     The last update as of FY 2015 was reported at the 23rd session in June 2016 (Japanese, English).

The second round
   There is no change in the number of suspected/confirmed thyroid cancer cases at 71 (32 males and 39 females). Surgical cases remain at 56 (55 papillary thyroid cancer and 1 "other" thyroid cancer) . 
     The most recent FY2020 update of the second round data was previously reported at the 42nd session (Japanese, English), with the brief update released at the last session showing the latest surgical data.

The third round
     There is no change in data with 31 suspected/confirmed thyroid cancer cases (13 males and 18 males), of which 29 were surgically confirmed as papillary thyroid cancer. The final report from the 39th session in August 2020 (JapaneseEnglishwas updated as of FY2020 and reported at the 42nd session in July 2021 (Japanese, English).
The fourth round
    The fourth round, originally scheduled from April 1, 2018 through March 31, 2020, is now complete. The final report was presented to the 20th TUE Subcommittee session on March 20, 2023. There are 39
 suspected or confirmed thyroid cancer cases, of which 34 have been surgically confirmed as papillary thyroid cancer. 

The fifth round
    The fifth round targets 252,915 individuals, excluding about 21,000 born in FY 1996 (April 2, 1996 to April 1, 1997) and about 20,000 born in FY 1997 (April 2, 1997 to April 1, 1998) who are earmarked for the Age 25 Milestone Examination in FY 2021-2022. (It has previously been discussed how this exclusion skews age distribution graphs to the left.)
    The COVID-19 restrictions have had a significant impact on the progress of the fifth round which began in April 2020: school closures initially halted the school-based screening, and a burden on medical facilities reduced participation in the confirmatory examination. [Note: The fifth round was originally earmarked for FY 2020-2021 (April 2, 2020 to March 31, 2022), but the pandemic has forced an extension of the screening period by one year as described in this proposal: Elementary and middle school students from FY 2020 municipalities will undergo the TUE in FY 2020-2021, while FY 2021 municipalities will be pushed to FY 2022. For high school students, the TUE will be conducted in FY 2021-2022 with the exception of those who were already examined in FY 2020.] 
     The sixth round is expected to return to a two-year screening cycle beginning April 2023.

     As of September 30, 2022, 89,094 participated in the primary examination, including 8,889 new participants, and its participation rate slightly increased from 31.7% to 35.2%, finally exceeding half of the fourth-round participation rate. Participation rates by age group changed from 52.7% to 58.4% in ages 8-11, from 38.1% to 43.3% in ages 12-17, and from 10.6% to 10.8% in ages over 18: changes in the first two age groups probably reflecting progress of the school-based screening. The primary examination results only increased by 6,475 to 82,368 and the number of "B" assessment, which qualifies for the confirmatory examination, only increased by 62 to 1,001
     Of sixty-two who newly participated in the confirmatory examination, 6 underwent FNAC, and 3 females were newly diagnosed with suspected thyroid cancer. Their ages-at-exposure include ages 1, 4, and 9 years, and all 3 are from the FY 2020 municipalities. Their previous results include 1 with A1, 1 with A2 cyst, and 1 with B. 
     Nine participants — seven from FY 2020 and two from FY2021 municipalities — have been confirmed with papillary thyroid cancer after undergoing surgery.

   In summary, as of September 30, 2022, the number of suspected or confirmed thyroid cancer cases for the fifth round is 26, of which 16 have been surgically confirmed as papillary thyroid cancer. 
   The previous results from the fourth round are as follows: 20 with "A" (8 with A1, 11 with A2 cysts, 1 with A2 nodules), 4 with "B," and 2 with no prior result. 

Age 25 Milestone Screening
    In the Age 25 Milestone Screening, each screening year targets a cohort turning 25 during each fiscal year, and the results are reported every 6 months. The most recent implementation schedule available in English is from September 2020, which was reported to the 41st session of the Oversight Committee and can be found here(No one is supposed to undergo a regular TUE within 2 years of becoming eligible for the Age 25 Milestone Screening.) Although each fiscal-year screening is earmarked for those turning 25 during that fiscal year, participants can take part in the screening anytime up to the year before they become eligible for the Age 30 Milestone Screening. 
Note: Transition of each FY birth cohort to the Age 25 Milestone Screening reduces a target population for the main TUE. This reduction began in the third round conducted during FY 2016-2017, which excluded the FY 1992 and 1993 cohorts in anticipation of the upcoming Age 25 Milestone Screening. With each FY birth cohort including about 22,000 individuals, this is a sizable reduction which continues as the TUE target population ages. An exception is an increase from 367,637 for the first round to 381,237 for the second round which is due to an inclusion of those who were in utero at the time of the accident). From then on, it has decreased to 336,667 for the third round, 294,228 for the fourth round, and now 252,902 for the fifth round.

    The results reported this time are from the data up to September 30, 2022, including the secondary examination results for the FY1996 cohort which were excluded in the last report. Also in FY2022, those born in FY1992 became eligible to participate in the Age 30 Milestone Screening, but no data was reported on this.
     Target population from the FY1992 to FY1996 cohorts remains stable at 108,711. The primary examination participation increased by 399 to total participants of 10,240, and the participation rate, which had previously dipped due to a larger denominator from the target population increase, recovered from 9.1% to 9.4%.
    An additional 46 participants received "B" assessment in the primary examination this time. Together with 74 from the FY1996 cohort who were previously excluded from the confirmatory examination results, 120 more were added to the confirmatory examination qualifiers, making the total of 550. Eighty-three more participated in the confirmatory examination, making the total participants 436, and 416 (72 more than last time) have the final results. After FNAC was conducted in 5 individuals (with total FNAC cases of 36), 3 females were diagnosed with suspected thyroid cancer. Their ages at exposure were 14, 14, and 15 years, and their prior screening results were 1 with A1, 1 with B, and 1 with no prior screening. There is no residence location information available for these cases because the regional data is only  reported for the primary examination.

     In summary, the number of suspected or confirmed thyroid cancer cases from the Age 25 Milestone Screening increased by 3 to 19. The results from the prior screening are: 5 with "A" (1 with A1, 1 with A2 nodules, 3 with A2 cysts), 4 with "B" and 10 with no prior screening.
     One new surgical case, confirmed as papillary thyroid cancer, was added, and the number of surgically confirmed thyroid cancer increased to 11, including 10 papillary thyroid cancers and 1 follicular thyroid cancer.

Expected upcoming changes in the dataset   
     There are two factors inherent to the implementation structure of the TUE, leading to a smaller dataset with each screening cycle. One is a reduced size of target population and the other is a decline in participation rates, both of which are already being observed and expected to progress.
     As described above, a shift of a cohort to the Milestone Screening (Age 25, Age 30, etc.) with time reduces the target population in each successive screening cycle. Furthermore, school-based screening conducted through high school slows down with each cohort graduating from high school. It will eventually come to a natural halt when the youngest cohort born in FY2011 (between April 2, 2011 and April 1, 2012) finishes high school in 2029. It should be noted that the school-based screening is completely voluntary, no less the TUE itself.
     Convenience of the school-based screening contributes to a higher participation rate for ages up to 18 than past age 18. This is clearly shown in the most recent participation rates by age reported in this post: 58.4% in ages 8-11, 43.3% in ages 12-17, and 10.8% in ages over 18 in the fifth round, and 9.4% for the Age 25 Milestone Screening. 
     It is critical to recognize these expected changes for future datasets when reviewing the TUE data because they cast doubt on reliability and integrity of the TUE data itself and any analysis conducted. Retrieval of "missing data" due to "unreported cases" at any age is being attempted by matching the TUE data with regional (up to 2015) and national (from 2016 on) cancer registry data. For instance, reconciliation with the most recently available national cancer registry data up to 2018  (document from the 19th Subcommittee session) revealed 43 cases from the cancer registry, which are not included in the official TUE count. This is an increase from 27 cases up to 2017 (reported to the 18th Subcommittee session). Nonetheless the cancer registry is far from fool-proof because patients who move their official residence registry outside Fukushima are not reported as Fukushima cases.

Summary of the results from the previous screening 
    Below is the summary of the previous screening results for the suspected/confirmed thyroid cancer cases. This information, already mentioned above except for the second round, can be difficult to locate in print. In particular, a breakdown of the "A2" assessment is only verbally reported during the Oversight Committee sessions. 

"A1": no ultrasound findings. 
"A2": ultrasound findings of nodules ≤ 5.0 mm and/or cysts ≤ 20.0 mm. 
"B": ultrasound findings of nodules  5.1 mm and/or cysts  20.1 mm.

    Having previous assessments of "A1" or "A2 cysts" means there were no precancerous lesions during the previous screening, i.e., cancer supposedly appeared since the previous screening. (Note: FMU claims that the cancerous lesions did not newly appear but already existed yet "invisible" during the previous screening.)
  • Second round (71 cases): 33 cases with A1, 32 cases with A2 (7 nodules and 25 cysts), 5 cases with B, and 1 case previously unexamined
  • Third round (31 cases):  7 cases with A1, 14 cases with A2 (4 nodules and 10 cysts), 7 cases with B, and 3 cases previously unexamined
  • Fourth round (39 cases): 6 cases with A1, 20 cases with A2 (6 nodules, 13 cysts, and 1 nodule & cyst), 9 cases with B, and 4 cases previously unexamined
  • Fifth round (26 cases): 8 case with A1, 12 cases with A2 (11 cysts and 1 nodule & cyst), 4 cases with B, and 2 cases previously unexamined
  • Age 25 Milestone Screening (19 cases): 1 case with A1, 4 cases with A2 (1 nodule and 3 cyst), 4 cases with B, and 10 cases previously unexamined



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