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 session. This 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 post, Sobue, 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 321: 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, 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 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 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 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.
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
