Overview
On November 12, 2024, the 53rd 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, 2024 for the Thyroid Ultrasound Examination (TUE). What was reported include 3-month worth of data for the fifth and sixth rounds.
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 session discussed in this post, the official translation will be available here in the foreseen future. 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: 2 new cases diagnosed as suspicious or malignant.
- The sixth round: 5 new cases diagnosed as suspicious or malignant. The age/sex distribution reported for the first time.
- No new surgical cases.
- Total number of suspicious or malignant cases has increased by 7 to 345: 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, 48 in the fifth round, 11 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 is unchanged at 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.
Clinicopathological Data on 220 Surgical Cases
Also reported at this session of the Oversight Committee as well as the 23rd Session of the Thyroid Ultrasound Examination Review Subcommittee (TUE Subcommittee herein) held 3 days later was the clinicopathological data on 220 surgical cases. The 220 cases, operated on at Fukushima Medical University (FMU) Hospital up to September 2021, are from the first through the fourth rounds as well as the Age 25+ Survey.
The reporting was done at this timing after the same data had been published online on October 14, 2024 in Thyroid, an official journal of the American Thyroid Association. Unfortunately it is not open access, but some of the details are discussed in the Japanese post (here) especially in comparison with the previously reported 180 and 125 surgical cases.
The 125 surgical case data (see this post) warrant a special mention since the 2016 international symposium it was presented at was a pivotal moment in retrospect that led to formation of the international expert group Thyroid Monitoring after Nuclear Accidents (TM-NUC) which eventually gave rise to an international consensus to discourage mass thyroid screening after future nuclear accidents. (See the SHAMISEN recommendations written up here and as PDF.) Interestingly TM-NUC was fully funded by the Japanese government. This chain of events was explained in another Japanese post here as well as this English post, and how this consensus is partly based on confusing and contorted data analysis by FMU has been discussed in an English post here.
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.)
In accordance with the 2022 reclassification of the cribriform-morular variant of PTC as cribriform-morular thyroid cancer (CMTC), an adjustment was made in the table. Four cases from the first round were are now listed under CMTC.
The official count, as reported above and also in the summary document shown in the next section, is 345 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 with an addition of 2019 data at the 23rd session of the TUE Subcommittee), the count increases to 427 cytologically suspicious or malignant and 350 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.
#53 Status of the Thyroid Ultrasound Examination Results (November 12, 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 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, 2024, the total number of participants in the primary examination increased only by 1 to 113,960. The participation rate is unchanged at 45.1% The primary examination results increased by 10 to 113,960 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 3, and four, all from FY2021 municipalities, underwent FNAC (fine-needle aspiration cytology) with two being newly diagnosed with suspicion of thyroid cancer. They are both from Hamadori. One is a male who was age 3 at exposure and the other a female who was age 2. Their previous results are A2 cyst and A2 cyst/nodule.
There was no new surgical case reported.
In summary, as of June 30, 2024, the number of suspicious or malignant cases for the fifth round is 48, of which 42 have been surgically confirmed as papillary thyroid cancer. The previous results from the fourth round are as follows: 36 with "A" (11 with A1, 21 with A2 cysts, 1 with A2 nodule, 3 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 (48 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 211,901 which is 41,037 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 June 30, 2024, the number of primary examination participants increased by 2,932 to a total of 45,348, which increased the participation rate from 20.0% to 21.4%. The results have been finalized in 42,987, and 630 received the B assessment with a new addition of 48.
Of 630 eligible, 109 newly underwent the confirmatory examination for total of 352 (55.9%) , and 127 newly received the finalized results. Ten (7 from the FY2022 and 3 from the FY2023 municipalities) newly underwent the FNAC and five (1 male and 4 females) were found to have suspicious or confirmed thyroid cancer, making the total suspected/confirmed thyroid cancer cases to be 11.
With the number of cases exceeding 10, this is the first time the reporting was made for the sixth round on the age and sex distribution of suspicious thyroid cancer cases as well as the previous results from the fifth round. Three of 11 cases were males (ages-at-exposure 0, 1 and 5) and the remaining 8 were females (ages-at-exposure 1, 3, 4, 5, 5, 8, 8, 9). Their previous results are as follows: 6 with "A" (2 with A1, 3 with A2 cysts, 1 with A2 nodules/cysts), 2 with "B," and 3 with no prior result. No geographical information was reported.
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.
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 (48 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 (11 cases): 2 cases with A1, 4 cases with A2 (3 cysts and 1 nodules & cysts), 2 cases with B, and 3 cases previously unexamined
- 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
