Fukushima Thyroid Examination February 2024: 274 Surgically Confirmed as Thyroid Cancer Among 328 Cytology Suspected Cases


Note: From this post onward, the terms "Age 25+ Survey" and "Age 30+ Survey" are to replace "Age 25 Milestone Screening" and "Age 30 Milestone Screening," in accordance with the terms used in official translation of the reports

Overview

     On February 2, 2024, the 50th 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, 2023) from the fifth and sixth rounds as well as the Age 25+ and Age 30+ Surveys of the Thyroid Ultrasound Examination (TUE).  It amounts to a 3-month worth of data since the previous session held on November 24, 2023 (English translation here) for the fifth and sixth rounds, and a 6-month worth of data since the July 20, 2023 session (English translation here) for the biannually reported Age 25+ and Age 30+ Surveys. 

     Official translations of the reports from the Oversight Committee are available on the Materials and Minutes of Prefectural Oversight Committee Meetings page (link) on the website of Radiation Medical Science Center of the Fukushima Health Management Survey (RMSC/FHMS). After markedly delayed publishing of English translations in the last few years, it has finally caught up: As of today official English translations are available up to the 49th session. This website also shows an overview of the FHMS and the TUE itself, which might be informative to those unfamiliar with them.


Highlights
  • The fifth round: 4 new cases diagnosed as suspicious or malignant, and 7 new surgical case.
  • The sixth round: no confirmatory examination results available.
  • Age 25+ Survey: 1 new case diagnosed as suspicious or malignant and 3 new surgical cases.
  • Age 30+ Survey: 2 new cases diagnosed as suspicious or malignant and 2 new surgical cases.
  • Total number of suspicious or malignant cases has increased by 7 to 328116 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, 43 in the fifth round, and 23 in the Age 25+ Survey and 5 in the Age 30+ Survey.
  • Total number of surgically confirmed thyroid cancer cases has increased by 12 to 274 (101 in the first round, 56 in the second round, 29 in the third round, 34 in the fourth round, 34 in the fifth round, 17 in the Age 25+ Survey and 3 in the Age 30+ Survey.

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 328 suspicious or malignant cases and 274 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 406 cytologically suspicious or malignant and 336 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 nine-page summary of the first through sixth rounds as well as the Age 25+ and Age 30+ Surveys, "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.
     Below is a brief descriptive summary of each round, regardless of the update status, provided for easy reference.

The first round
     There is no change in data with 116 suspicious or malignant cases (39 males and 77 females), of which 102 underwent surgery which confirmed 1 case with 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 suspicious or malignant cases at 71 (32 males and 39 females). Surgically confirmed 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 suspicious or malignant 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
    There is no change in data with 
39 suspicious or malignant cases (17 males and 22 females), of which 34 have been surgically confirmed as papillary thyroid cancer. The final report was presented to the 20th TUE Subcommittee session on March 20, 2023 but not independently to the Oversight Committee. Since the meeting materials from the TUE Subcommittee are not officially translated, the final report will also not be translated. However, it is identical to the version presented to the 46th session in December 2022 whose translation can be found here.

The fifth round (updated this time)
    The fifth round targets 252,938 individuals who were born in FY 1998-2011. Originally earmarked for FY 2020-21 (April 2, 2020 to March 31, 2022), its implementation was extended by 1 year due to the COVID-19 pandemic. With only a very small increase of new participants in the primary examination and no new participants eligible for the confirmatory examination, the fifth round finally appears to be near completion although it might be a while before the final version of the results is released. (For reference, the final results of the fourth round weren't released until 3 years past its scheduled completion date of March 2020.)  

     As of September 30, 2023, the total number of participants in the primary examination was 113,941 with an addition of 4 new participants (3 residing outside Fukushima). There are no changes in its participation rates either overall or by age group: 45.0% overall, 74.0% in ages 8-11, 57.8% in ages 12-17, and 11.2% in ages over 18. The primary examination results increased by 9 to 113,941 with the completion rate of 100%, and there was no new "B" assessment, and the number of individuals qualifying for the confirmatory examination remains at 1,346

    The number of new participants in the confirmatory examination was 75, and 7 underwent FNAC with 4 being newly diagnosed with suspicion of thyroid cancer. This included 1 male (ages-at-exposure of 1 year) and 3 females (ages-at-exposure of 3, 4, and 7 years). One female was from the FY 2020 municipalities and the rest from the FY2021 municipalities. Their previous results included 1 with A1 and 3 with A2 cyst.  
 
    There were 7 new surgical cases with 4 from the FY2020 and 3 from the FY2021 municipalities. All 7 cases were confirmed as papillary thyroid cancer.

    In summary, as of September 30, 2023, the number of suspicious or malignant cases for the fifth round is 43, of which 34 have been surgically confirmed as papillary thyroid cancer. The previous results from the fourth round are as follows: 31 with "A" (10 with A1, 20 with A2 cysts, 1 with A2 nodules/cysts), 6 with "B," and 6 with no prior result. 

    The regional distribution of 43 suspicious or malignant cases showed that 2 each of 4 new cases were from Naka-dori and Hama-dori. Overall, 6 were from the evacuation zone, 26 from Naka-dori, 8 from Hama-dori, and 3 from Aizu, and the proportions against the primary examination participants were 0.04%, 0.04%, 0.04%, and 0.02% respectively.

     The fifth round now has more suspicious or confirmed cases than the fourth round (43 vs. 39), and the FMU officials explained that this was due to a natural shift of the target population into ages at which thyroid cancer frequency begins to increase.  Also there are now more females diagnosed with suspicion of thyroid cancer, and thyroid cancer incidence is usually higher in females. Aside from any consideration for possible radiation effects, natural sex- and age-related changes in incidence make a clear understanding of the situation more complicated, which is further complicated by any more "unreported" cases which have not come to the surface.

The Sixth Round

     The sixth round began in April 2023 with a target population of 211,875 which is 41,063 fewer than the fifth round, reflecting an additional exclusion of those born in FY 1998-1999 who will transition to the Age 25+ Survey. 

     As of September 30, 2023, the number of primary examination participants increased by 13,348 to a total of 18,304, which increased the initial participation rate of 2.3% to 8.6%. Of 9,978 whose results are available, 118 received the B assessment. There has been very little progress of the confirmatory examination, and its results were not reported.

[Important note: Transition of each FY birth cohort to the Milestone Screening (Age 25+ Survey and so on) reduces a target population for the main TUE. This reduction began in the third round conducted during FY 2016-2017, which excluded the FY 1992-1993 cohorts in anticipation of the upcoming the Age 25+ Survey. 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, 252,938 for the fifth round, and now 211,865 for the sixth round. The January 2021 post explains how this ongoing transition skews age distribution graphs to the left.]

The Age 25+ Survey
    In the Age 25+ Survey, each screening year targets a cohort turning 25 during that fiscal year, and the results are reported every 6 months. The most recent implementation schedule available in English is from March 2023, which was reported to the 48th 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+ Survey.) 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+ Survey. 

    The results reported this time are from the data up to September 30, 2023, including the results for the newly eligible FY1997 cohort. Although the FY1992 cohort is still included in the results, there is no change in data since this cohort has transitioned to the Age 30+ Survey .
     An addition of the FY1997 cohort increased the target population from 108,711 to 129,006. The primary examination participation increased only by 86 to total participants of 11,867, and the participation rate slightly increased from 9.1% to 9.2%.
    An additional 12 participants received "B" assessment in the primary examination this time,  making the total eligible for the confirmatory examination to be 647. With 22 newly participating in the confirmatory examination, a total of 545 participated and the results have been finalized for 535 (35 more than last time). After the FNAC was conducted in 6 individuals (with total FNAC cases of 49), 1 female (age-at-exposure of 14 years) was diagnosed with suspicion of thyroid cancer. She did not participate in the prior screening. There is no residence location information available for the case because the regional data is only reported for the primary examination.

     In summary, the number of suspicious or malignant cases from the Age 25+ Survey increased by 1 to 23. 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 14 with no prior screening.

     Three new surgical cases were added and confirmed as papillary thyroid cancer, and the number of surgically confirmed thyroid cancer increased to 17, including 16 papillary thyroid cancers and 1 follicular thyroid cancer.

Age 30+ Survey
     The Age 30+ Survey, began in April 2022, targeting 22,625 born in FY1992. The second set of results as of September 30, 2023 were reported this time and included the average age and tumor diameter for the suspected/confirmed thyroid cancer cases.

    The primary examination participants increased by 47 to 1,571, slightly increasing the participation rate from 6.7% to 6.9%. The results are confirmed in 1,562, and 8 more received the B assessment increasing the number of participants eligible for the confirmatory examination to 134. With 32 newly undergoing the confirmatory examination, its participants increased to 107, of which 96 had the results finalized with a new addition of 38. Eight underwent the FNAC, and 2 females were diagnosed with suspicion of thyroid cancer. The average age information newly released this time (average age-at-exposure of 18 with a range of 18 to 18) shows that they were both 18 at exposure.

     In summary, the number of suspicious or malignant cases from the Age 30+ Survey increased by 2 to 5. Although age distribution graph has not been released due to a small number of cases, the average age information reveals that all 5 were 18 at the time of the accident. The average tumor diameter was also newly reported to be 12.6 mm (range: 9.9 mm to 18.6 mm). This is smaller than 14.2 mm (range: 5.3 mm to 49.9 mm) in the Age 25+ cases, but this is likely accounted for by the presence of a follicular cancer case in the Age 25+ data which contributed to a large maximum diameter of 49.9 mm. In fact, the minimum diameter in the Age 30+ cases is almost twice as large as the Age 25+. 
     
     Also newly reported this time are the results from the prior screening: 1 with "A" (1 with A2 cysts), 1 with "B" and 3 with no prior screening.

Expected 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 (see above) 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 Age 25+ and Age 30+ (and so on) Surveys with time reduces the target population in each successive screening cycle. Furthermore, school-based screening conducted through high school dwindles 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 higher participation rates 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: 74.0% in ages 8-11, 57.8% in ages 12-17, and 11.2% in ages over 18 in the fifth round, 9.2% for the Age 25+ Survey, and 6.9% for the Age 30+ Survey. 
     It is critical to recognize these expected changes for future datasets when reviewing the TUE data because they cast doubt on reliability and/or integrity of the TUE data itself and any analysis conducted using such data. 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. 

Definition
"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 (43 cases): 10 cases with A1, 21 cases with A2 (20 cysts and 1 nodule & cyst), 6 cases with B, and 6 cases previously unexamined
  • Age 25+ Survey (23 cases): 1 case with A1, 4 cases with A2 (1 nodule and 3 cyst), 4 cases with B, and 14 cases previously unexamined
  • Age 30+ Survey (5 cases): 1 case with A2 (1 cyst), 1 case with B, and 3 cases previously unexamined

      

  

Fukushima Thyroid Examination December 2023: 262 Surgically Confirmed as Thyroid Cancer Among 321 Cytology Suspected Cases

 

Overview

     On November 24, 2023, the 49th 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 June 30, 2023) from the fifth round and the newly started sixth round of the Thyroid Ultrasound Examination (TUE).  It amounts to 3-month worth of data since the previous session held on July 20, 2023 for the fifth round, and first-time reporting of the sixth round which commenced in April 2023. 

     Official translations of the reports from the Oversight Committee will eventually appear on the Materials and Minutes of Prefectural Oversight Committee Meetings page (link) on the website of Radiation Medical Science Center of the Fukushima Health Management Survey (RMSC/FHMS). As of today, official English translations are available up to the 47th sessionThis website also shows an overview of the FHMS and the TUE itself, which might be informative to those unfamiliar with them.

New Member Rosters and the Subcommittee Summary

     This was the first session for a new two-year term beginning on August 1, 2023, which makes this the seventh term of the Oversight Committee which was started in 2011, and the new member roster showed 5 new members. Also released was a new roster for the fifth term of the Thyroid Examination Evaluation Subcommittee (herein the TUE Subcommittee) with 3 new members. Some details regarding the replaced members are covered in the Japanese post (automatic English translation is mostly reasonable for the applicable content), but an oust of Takahiro Sobue warrants a special mention. 

     As covered in the previous postSobue, a cancer statistician from Osaka University, expressed a strong disagreement with the conclusion of the summary draft which was presented to the 21st session of the TUE Subcommittee (aka the very last session of the 4th term) in July 2023. This summary draft covers up to the fourth round and concluded that no consistent dose response relationship was seen between the exposure dose and the thyroid cancer detection rate. However, Sobue did not agree that such a definite conclusion could be drawn based on the data and analyses provided. The revised summary presented this time reflects discussions from the 21st session including Sobue's dissents. Just to show the extent of the revision which is mostly on page 4 of both draft and revised versions, a screenshot of the respective part of the summary draft (in Japanese) is shown here.

        And this is the same part in the revised draft with the added content highlighted, which reflects Sobue's opinion that there was a difficulty in drawing conclusions on the relationship between thyroid cancer and radiation due to an insufficient control of the confounding factor. 

Highlights
  • The fifth round: 5 new cases diagnosed as suspicious or malignant, and 1 new surgical case.
  • The sixth round: just started and no confirmatory examination results available.
  • Total number of suspected/confirmed thyroid cancer has increased by 5 to 321116 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, 39 in the fifth round, and 22 in Age 25 Milestone Screening, and 3 in Age 30 Milestone Screening.
  • Total number of surgically confirmed thyroid cancer cases has increased by 14 to 262 (101 in the first round, 56 in the second round, 29 in the third round, 34 in the fourth round, 27 in the fifth round, 14 in Age 25 Milestone Screening and 1 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 321 suspected/confirmed and 262 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 399 cytologically suspected/confirmed and 324 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 nine-page summary of the first through sixth rounds as well as the Age 25 and Age 30 Milestone Screenings, "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.
     Below is a brief descriptive summary of each round, regardless of the update status, provided for easy reference.

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
    There is no change in data with 
39 suspected/confirmed thyroid cancer cases (17 males and 22 females), of which 34 have been surgically confirmed as papillary thyroid cancer. The final report was presented to the 20th TUE Subcommittee session on March 20, 2023 but not independently to the Oversight Committee. Since the meeting materials from the TUE Subcommittee are not officially translated, the final report will also not be translated. However, it is identical to the version presented to the 46th session in December 2022 whose translation can be found here.

The fifth round (updated this time)
    The fifth round targets 252,938 individuals who were born in FY 1998-2011. Originally earmarked for FY 2020-21 (April 2, 2020 to March 31, 2022), its implementation was extended by 1 year due to the COVID-19 pandemic. With only a two-digit increase in participants, the fifth round finally appears to be near completion although it might be a while before the final version of the results is released. (For reference, the final results of the fourth round weren't released until 3 years past its scheduled completion date of March 2020.)      

     As of June 30, 2023, the total number of participants in the primary examination was 113,937 with an addition of 85 new participants (41 residing outside Fukushima). There are no changes in its participation rates either overall or by age group: 45.0% overall, 74.0% in ages 8-11, 57.8% in ages 12-17, and 11.2% in ages over 18. The primary examination results increased by 5,682 to 113,932 and the number of "B" assessment, which qualifies for the confirmatory examination, increased by 47 to 1,346

    The number of new participants in the confirmatory examination was also smaller at 47, and 12 underwent FNAC with 5 being newly diagnosed with suspected thyroid cancer. This included 2 males (ages-at-exposure of 4 and 10 years) and 3 females (ages-at-exposure of 2, 4, and 6 years). One male and 1 female were from the FY 2020 municipalities and 1 male and 2 females were from the FY2021 municipalities. Their previous results included 1 with A1, 3 with A2 cyst, and 1 with no prior examination.  
 
    There was only 1 new surgical case in from the FY2020 municipalities which was confirmed as papillary thyroid cancer.

    In summary, as of June 30, 2023, the number of suspected or confirmed thyroid cancer cases for the fifth round is 39, of which 27 have been surgically confirmed as papillary thyroid cancer. The previous results from the fourth round are as follows: 27 with "A" (9 with A1, 17 with A2 cysts, 1 with A2 nodules/cysts), 6 with "B," and 6 with no prior result. 

    The regional distribution of 39 suspected/confirmed thyroid cancer cases showed that 6 were from the evacuation zone, 24 from Naka-dori, 6 from Hama-dori, and 3 from Aizu. The proportions against the primary examination participants were 0.04%, 0.04%, 0.02%, and 0.03% respectively.

The Sixth Round (newly reported)

     The sixth round just began in April 2023 with a target population of 211,865 which is 41,073 fewer than the fifth round, reflecting an additional exclusion of those born in FY 1998-1999 who will transition to the Age 25 Milestone Screening. 

     As of June 30, 2023, only 4,956 participated in the primary examination with the initial participation rate of 2.3%. Of 208 whose results are available, 4 received the B assessment none of who underwent the confirmatory examination.    

[Important note: Transition of each FY birth cohort to the 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 1992-1993 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, 252,938 for the fifth round, and now 211,865 for the sixth round. The January 2021 post explains how this ongoing transition skews age distribution graphs to the left.]

Expected 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 (see above) 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 dwindles 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 higher participation rates 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: 74.0% in ages 8-11, 57.8% in ages 12-17, and 11.2% in ages over 18 in the fifth round, 9.1% for the Age 25 Milestone Screening, and 6.7% for the Age 30 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 using such data. 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. 

Definition
"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 (39 cases): 9 cases with A1, 18 cases with A2 (17 cysts and 1 nodule & cyst), 6 cases with B, and 6 cases previously unexamined
  • Age 25 Milestone Screening (22 cases): 1 case with A1, 4 cases with A2 (1 nodule and 3 cyst), 4 cases with B, and 13 cases previously unexamined
  • Age 30 Milestone Screening (3 cases): unknown

      

  

Fukushima Thyroid Examination July 2023: 261 Surgically Confirmed as Thyroid Cancer Among 316 Cytology Suspected Cases

Overview

     On July 20, 2023, the 48th 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 March 31, 2023) from the fifth round as well as the biannually reported Age 25 and Age 30 Milestone Screenings of the Thyroid Ultrasound Examination (TUE).  It amounts to 6-month worth of data since the previous session held on March 22, 2023 for the fifth round and the Age 25 Milestone Screening, and first-time reporting of the Age 30 Milestone Screening. This was the last session for the existing committee members whose two-year term ended on July 31, 2023.

    Official translations of the reports from the Oversight Committee will eventually appear on the Materials and Minutes of Prefectural Oversight Committee Meetings page (link) on the website of Radiation Medical Science Center of the Fukushima Health Management Survey (RMSC/FHMS). As of today, official English translations are available up to the 43rd session (PDF link)This website also shows an outline of the FHMS and TUE itself, which might be informative to those unfamiliar with them.

Special Note: A Draft Summary by the Thyroid Examination Evaluation Committee

     Only 8 days later on July 28, 2023, the 21st session of the Thyroid Examination Evaluation Subcommittee (herein TUE Subcommittee) was held. The back-to-back schedule also marked the end of a two-year term for the existing subcommittee members who all served two consecutive terms. This last subcommittee session was notable for a hasty presentation of a draft version of a summary report covering the first through fourth rounds prepared by Subcommittee Chair Gen Suzuki. 

    Some of the subcommittee members expressed disagreement with parts of the summary draft. The strongest criticism came from Tomotaka Sobue who disagreed with the phrase that no consistent dose response relationship was seen between the exposure dose and thyroid cancer detection rate. 

    The TUE was initially rolled out region by region over several years, and timing of participation in the TUE is one of the confounding factors which were matched in the case control analyses conducted by FMU. Sobue explained that when the analyses were not limited to specific regions (as in analyses 3-1, 3-2, 3-3, 3-7, 3-8, 3-9), odds ratios appeared to increase suggestive of dose response, albeit lack of statistical significance. However, the analyses limited to specific regions (3-4, 3-5, 3-6) showed a flatter or negative response, and according to Sobue this discrepancy implies an inadequate control of what is considered the biggest confounding factor in the analyses: timing of participation in the TUE. 

    In Sobue's opinion the phrase should more accurately reflect the fact that there was a difficulty to draw conclusions on the relationship between thyroid cancer and radiation due to insufficient control of the confounding factor. (It should be noted that competence of the analysis by FMU is not much different from the second-round analysis covered in this 2019 post. The summary draft for the second round also met criticisms which were not incorporated into the final version but published as a separate document, both of which were presented at the 35th Session of the Oversight Committee held in July 2019.)

Highlights
  • The fifth round: 8 new cases diagnosed as suspicious or malignant, and 10 new surgical cases.
  • Age 25 Milestone Screening: 3 new cases diagnosed as suspicious or malignant and 3 new surgical cases.
  • Age 30 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 14 to 316116 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, 34 in the fifth round, and 22 in Age 25 Milestone Screening, and 3 in Age 30 Milestone Screening.
  • Total number of surgically confirmed thyroid cancer cases has increased by 14 to 261 (101 in the first round, 56 in the second round, 29 in the third round, 34 in the fourth round, 26 in the fifth round, 14 in Age 25 Milestone Screening and 1 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 316 suspected/confirmed and 261 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 394 cytologically suspected/confirmed and 323 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
    An eight-page summary of the first through fifth rounds as well as the Age 25 and Age 30 Milestone Screenings, "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
    There is no change in data with 
39 suspected/confirmed thyroid cancer cases (17 males and 22 females), of which 34 have been surgically confirmed as papillary thyroid cancer. The final report was presented to the 20th TUE Subcommittee session on March 20, 2023.  

The fifth round
    The fifth round targets 252,938 individuals who were born in FY 1998-2011. Originally earmarked for FY 2020-21 (April 2, 2020 to March 31, 2022), its implementation was extended by 1 year due to school closures and an extraordinary burden on medical facilities from the COVID-19 pandemic which began in March 2020. (The sixth round has returned to a two-year screening cycle beginning April 2023.) Note that the target population has been reduced by one-third compared to the first round, owing to the transition of individuals born in FY1992-1997 to the Age 25 and 30 Milestone Examinations. (The January 2021 post explains how this ongoing transition skews age distribution graphs to the left.)  

     As of March 31, 2023, 113,852 participated in the primary examination, including 24,758 new participants, and its participation rate increased from 35.2% to 45.0%. Participation rates by age group changed from 58.4% to 74.0% in ages 8-11, from 43.3% to 57.8% in ages 12-17, and from 10.8% to 11.2% in ages over 18, reflecting progress of the school-based screening in the first two age groups as well as persistently low participation of the over 18 age group. The primary examination results increased by 25,882 to 108,250 and the number of "B" assessment, which qualifies for the confirmatory examination, increased by 298 to 1,299

    Of 217 who newly participated in the confirmatory examination, 14 underwent FNAC, and 8 were newly diagnosed with suspected thyroid cancer. This included 3 males (ages-at-exposure of 7, 8, and 11 years) and 5 females (ages-at-exposure of 4, 6, 9, 11 and 12 years). Five were from the FY 2020 municipalities and 3 from the FY2021 municipalities. Their previous results include 3 with A2 cyst, 2 with B, and 3 with no prior examination.  
     
    There are an addition of 10 surgical cases in the fifth round — eight from FY 2020 and two from FY2021 municipalities — and all were confirmed with papillary thyroid cancer.

    In summary, as of March 31, 2023, the number of suspected or confirmed thyroid cancer cases for the fifth round is 34, of which 26 have been surgically confirmed as papillary thyroid cancer. The previous results from the fourth round are as follows: 23 with "A" (8 with A1, 14 with A2 cysts, 1 with A2 nodules/cysts), 6 with "B," and 5 with no prior result. 

    Additionally, the progress and results of the confirmatory examination by region were reported for the first time for the fifth round. Of 34 suspected/confirmed thyroid cancer cases, 5 were from the evacuation zone, 21 from Naka-dori, 5 from Hama-dori, and 3 from Aizu. The most populous Naka-dori had the highest number, but for all 4 regions the proportion against the primary examination participants was similar in the range of 0.02 to 0.03%

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 252,938 for the fifth round.

    The results reported this time are from the data up to March 31, 2023, including the results for the newly eligible FY1997 cohort. Although the FY1992 cohort is still included in the results, there is no change in data since this cohort has transitioned to the Age 30 Milestone Examination.
     An addition of the FY1997 cohort increased the target population from 108,711 to 129,007. The primary examination participation increased by 1,541 to total participants of 11,781, and the participation rate dipped from 9.4% to 9.1% due to a larger denominator from an increase of the target population.
    An additional 85 participants received "B" assessment in the primary examination this time,  making the total eligible for the confirmatory examination to be 635. With 85 newly participating in the confirmatory examination, a total of 635 participated and the results have been finalized for 500 (84 more than last time). After FNAC was conducted in 7 individuals (with total FNAC cases of 43), 3 females were diagnosed with suspected thyroid cancer. Their ages-at-exposure were 12, 13, and 14 years, and none had participated in 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 22. 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 13 with no prior screening.

     Three new surgical cases, confirmed as papillary thyroid cancer, were added, and the number of surgically confirmed thyroid cancer increased to 14, including 13 papillary thyroid cancers and 1 follicular thyroid cancer.

Age 30 Milestone Screening
    A second milestone screening, the Age 30 Milestone Screening, began in FY2022 starting in April 2022, targeting 22,626 born in FY1992. The first set of results as of March 31, 2023 were reported this time.

    Of 1,524 participants in the primary examination with participation rate of 6.7%, 126 had the B assessment becoming eligible for the confirmatory examination. Of 75 who underwent the confirmatory examination, the results have been finalized in 58. Five underwent FNAC, and 3 females were diagnosed with suspected/confirmed thyroid cancer. One of three has been confirmed with papillary thyroid cancer after undergoing surgery. No other details such as age, tumor diameter or prior examination results are available for them.


Expected 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: 74.0% in ages 8-11, 57.8% in ages 12-17, and 11.2% in ages over 18 in the fifth round, 9.1% for the Age 25 Milestone Screening, and 6.7% for the Age 30 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. 

Definition
"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 (34 cases): 8 cases with A1, 15 cases with A2 (14 cysts and 1 nodule & cyst), 6 cases with B, and 5 cases previously unexamined
  • Age 25 Milestone Screening (22 cases): 1 case with A1, 4 cases with A2 (1 nodule and 3 cyst), 4 cases with B, and 13 cases previously unexamined
  • Age 30 Milestone Screening (3 cases): unknown

      

  

Fukushima Thyroid Examination February 2024: 274 Surgically Confirmed as Thyroid Cancer Among 328 Cytology Suspected Cases

Note: From this post onward, the terms "Age 25+ Survey" and "Age 30+ Survey" are to replace "Age 25 Milestone Scree...