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 316: 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, 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 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 (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 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.
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.
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.
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
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