Overview
On August 2, 2024, the 52nd 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, 2024) for the Thyroid Ultrasound Examination (TUE). What was reported include 3-month worth of data for the fifth and sixth rounds and 6-month worth of data for the Age 25+ and 30+ Surveys.
Official English 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). For the current session discussed in this post, the official translation can be accessed here. 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: 1 new case diagnosed as suspicious or malignant, and 6 new surgical cases.
- The sixth round: 6 cases diagnosed as suspicious or malignant in the first reporting of the confirmatory examination results. No new surgical case reported.
- The Age 25+ Survey: No new case diagnosed as suspicious or malignant, and 1 new surgical case.
- The Age 30+ Survey: 1 new case diagnosed as suspicious or malignant, and one new surgical case.
- Total number of suspicious or malignant cases has increased by 8 to 338: 116 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, 46 in the fifth round, 6 in the sixth round, 23 in the Age 25+ Survey and 6 in the Age 30+ Survey.
- Total number of surgically confirmed thyroid cancer cases has increased by 8 to 284 (101 in the first round, 56 in the second round, 29 in the third round, 34 in the fourth round, 42 in the fifth round, 0 in the sixth round, 18 in the Age 25+ Survey and 4 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 338 suspicious or malignant cases and 284 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 416 cytologically suspicious or malignant and 346 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.
Age distribution bar graph errors
In the first round, one male who was 18 years old at the time of confirmatory examination had erroneously been reported to be 19 years old.
In the fifth round, one male who was 11 years old at the time of the accident had erroneously been reported to be 10 years old. He was 22 years old at the time of confirmatory examination but erroneously been reported to be 21 years old.
Explanation of these corrections is included in the official translation of the meeting materials (here). The corrections are also reflected in the summary document shown below.
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.
#52 Status of the Thyroid Ultrasound Examination Results (August 2, 2024) by Yuri Hiranuma on Scribd
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 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 (Japanese, English) was 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.
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 March 31, 2024, the total number of participants in the primary examination was 113,959 with an addition of 9 new participants (5 residing outside Fukushima), with the participation rate unchanged at 45.1% The primary examination results increased by 4 to 113,950 with a completion rate of 100%, and there was no new "B" assessment, and the number of individuals qualifying for the confirmatory examination remains unchanged at 1,346.
The number of new participants in the confirmatory examination was 16, and 3 underwent FNAC (fine-needle aspiration cytology) with one male who was age 6 at exposure being newly diagnosed with suspicion of thyroid cancer. He was from the FY2021 municipalities and from Hama-dori. His previous result was A2 nodule.
There were 6 new surgical cases from the FY2021 municipalities. Five cases were confirmed as papillary thyroid cancer and one case as another unspecified type of thyroid cancer.
In summary, as of March 31, 2024, the number of suspicious or malignant cases for the fifth round is 46, of which 42 have been surgically confirmed as papillary thyroid cancer. The previous results from the fourth round are as follows: 34 with "A" (11 with A1, 20 with A2 cysts, 1 with A2 nodule, 2 with A2 nodules/cysts), 6 with "B," and 6 with no prior result.
The fifth round now has more suspicious or confirmed cases than the fourth round (46 vs. 39), and the FMU officials explained at the 50th session 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 (updated this time)
The sixth round began in April 2023 with a target population of 211,892 which is 41,046 fewer than the fifth round, reflecting an additional exclusion of those born in FY 1998-1999 who transition to the Age 25+ Survey.
As of March 31, 2024, the number of primary examination participants increased by 7,981 to a total of 42,416, which increased the participation rate from 16.3% to 20.0%. The results have been finalized in 40,791, and 583 received the B assessment with a new addition of 200.
This is the first time the confirmatory examination results are reported or the sixth round. Of 583 eligible, 243 (41.8%) underwent the confirmatory examination and 171 or 70.4% had the results confirmed. Seven underwent the FNAC and six were found to have suspicious or confirmed thyroid cancer. Two were males and four were females whose age ranged from 0 to 9 years at the time of the accident. No other details, such as the age/sex distribution or geographical information, were reported this time probably because the number of cases is below 10.
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 which transitioned to 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 211,892 for the sixth round. The January 2021 post explains how this ongoing transition skews age distribution graphs to the left.
The Age 25+ Survey (updated this time)
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 available in the official translation of this meeting's materials here. For clarification, 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.
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 available in the official translation of this meeting's materials here. For clarification, 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 March 31, 2024, including the results for the newly eligible FY1998 cohort. Although the FY1992-1993 cohorts are still included in the results, there are essential changes in the results for these cohorts after transitioning to the Age 30+ Survey.
An addition of the FY1998 cohort increased the target population from 129,006 to 149,843. The primary examination participation increased by 736 to total participants of 12,603, but the increase in denominator led to a perceived decrease of the participation rate from 9.2% to 8.4%.
An additional 30 (26 from the FY1998 cohort) participants received "B" assessment in the primary examination this time, increasing the total number eligible for the confirmatory examination to be 677. However, the FY1998 cohort was excluded from the confirmatory examination results at this time, leading to an apparent discrepancy between the number of "B" assessment and those eligible for the confirmatory examination at 677 vs. 651. Only four newly participated in the confirmatory examination and no one underwent the FNAC. Thus there are no new suspicious or confirmed thyroid cancer cases.
In summary, the number of suspicious or malignant cases from the Age 25+ Survey remained at 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.
One new surgical case was added and confirmed as papillary thyroid cancer, and the number of surgically confirmed thyroid cancer increased to 18, including 17 papillary thyroid cancers and 1 follicular thyroid cancer.
Age 30+ Survey (updated this time)
The Age 30+ Survey, which began in April 2022, doubled the target population to 44,489 with an addition of 21,864 born in FY1993. The results as of March 31, 2024 were reported this time. Like the Age 25+ Survey, the FY1993 was excluded from the confirmatory examination results at this time, leading to a discrepancy between the number of "B" assessment and the number eligible for the confirmatory examination at 143 vs. 139.
The primary examination participants increased by 650 to 2,221, but the expansion of the denominator actually decreased the participation rate from 6.9% to 5.0%. The results are confirmed in 1,624, and 9 more received the B assessment increasing the number of participants eligible for the confirmatory examination to 143. With the FY1993 cohort excluded, 139 were eligible for the confirmatory examination and 11 newly participated. Three underwent the FNAC, and 1 female who was 18 years old at exposure was diagnosed with suspicion of thyroid cancer. Her previous result was A2 cyst.
In summary, the number of suspicious or malignant cases from the Age 30+ Survey increased by 1 to 6. Although age distribution graph has not been released due to a small number of cases, the average age information reveals that all 6 were 18 years old at the time of the accident. The results from the prior screening are: 2 with "A" (2 with A2 cysts), 1 with "B" and 3 with no prior screening.
One new surgical case was added and confirmed as papillary thyroid cancer. The number of confirmed thyroid cancer for the Age 30+ Survey is 4.
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.
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 (46 cases): 11 cases with A1, 23 cases with A2 (1 nodules, 20 cysts and 2 nodules & cysts), 6 cases with B, and 6 cases previously unexamined
- Sixth round (6 cases): Not reported
- Age 25+ Survey (23 cases): 1 case with A1, 4 cases with A2 (1 nodules and 3 cysts), 4 cases with B, and 14 cases previously unexamined
- Age 30+ Survey (6 cases): 2 cases with A2 (2 cysts), 1 case with B, and 3 cases previously unexamined
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