Overview
On September 1, 2022, the 45th 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, 2022) from the fourth and fifth rounds as well as the Age 25 Milestone Screening of the Thyroid Ultrasound Examination (TUE). Four and a half months have elapsed since the previous session held on May 13, 2022 (see previous post). This time 6 months worth of data was released, narrowing the widened gap between compilation and report dates of the data. (Only 3 months worth of data was reported at the last session despite the 7-month pause since the previous session. ) Still it's not the most recent data possible because FMU could have reported data through June.
As the data is usually compiled every 3 months, data between October 1, 2021 and December 31, 2021 was released separately as supplementary materials for both the fourth and fifth rounds in addition to data between October 1, 2021 and March 31, 2022. The Age 25 Milestone Screening data report, biannually released, is right on schedule. The fifth-round data reported this time includes the age and sex distribution of cancer cases for the first time. Also a brief update was reported on the second-round data with an addition of one surgical case.
The 45th session now consists of a full roster of 18 members with Nobuyuki Hirohashi of Hiroshima University replacing former Vice Chair Toshiya Inaba who abruptly resigned at the last session. Chair Noboru Takamura, a disciple of Shunichi Yamashita, has to be given credit for presiding over the meetings in a calm and logical manner despite his history of downplaying radiation health effects (see the previous post). This peaceful proceeding is in contrast to how dramatic and emotional it had been under the previous Chair Hokuto Hoshi who is now an LDP Upper House member representing Fukushima Prefecture. However, the moderator who is deputy chief of the Section of FHMS in the prefectural government has a strict and stern attitude during the press conference, severely and often rudely limiting question topics and time.
Official English translation (link) has been added for two more sessions and now is available up to the 42nd session (PDF link) of the Oversight Committee on this page of the website of the Radiation Medical Science Center of the Fukushima Health Management Survey (RMSC/FHMS). This website also shows an outline of the FHMS and TUE itself.
Highlights
- The second round: 1 new surgical case.
- The fourth round: 2 new cases diagnosed as suspicious or malignant, and 2 new surgical cases.
- The fifth round: 5 new cases diagnosed as suspicious or malignant, and 3 new surgical cases.
- Age 25 Milestone Screening: 3 new cases diagnosed as suspicious or malignant, and 4 new surgical cases.
- Total number of suspected/confirmed thyroid cancer has increased by 10 to 284: 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, 11 in the fifth round, and 16 in Age 25 Milestone Screening.
- Total number of surgically confirmed thyroid cancer cases has also increased by 10 to 236 (101 in the first round, 56 in the second round, 29 in the third round, 34 in the fourth round, 6 in the fifth round, and 10 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 284 suspected/confirmed and 236 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 362 cytologically suspected/confirmed and 297 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 seven-page summary of the first through fifth rounds as well as the Age 25 Milestone Screening, "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). There was one new surgical case in the second round which was diagnosed as papillary thyroid cancer, increasing the confirmed cancer cases to 56 (55 papillary thyroid cancer and 1 "other" thyroid cancer) as shown in the brief update.
The most recent FY2020 update of the second round data was previously reported at the 42nd session (Japanese, English).
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).
FMU is currently conducting an analysis of the third-round data, which has been presented to the TUE Subcommittee. FMU does not allow outside researchers to handle the data, yet FMU researchers conducting the analysis seem to lack expertise in statistical analysis which was apparent in the analysis of the second-round data (see this post). Recent TUE Subcommittee sessions have all but morphed into an "open statistical lecture series" with two subcommittee members, Tomotaka Sobue of Osaka University and Kota Katanoda of the National Cancer Center, giving advices and feedbacks on the analytical results presented by FMU.
At the 45th session of the Oversight Committee, a summary of the most recent TUE Subcommittee session--the 19th session held on August 1, 2022--was reported. The summary includes the interim results of the nested case control study which show an increased odds ratio at higher doses in any matching models (see pages 21, 25, 29, 33, 37, and so on, of the session summary) (added on September 19, 2022), but FMU claims the number of cases is too small and there is no statistical significance. Because only about half of the thyroid cancer cases have reconstructed doses, it was suggested that the third- and fourth-round data be analyzed together in order to increase the statistical power. This suggestion was approved by the Oversight Committee, and the joint analysis will begin when the final report of the fourth round becomes available. Although this might seem like a feasible idea, it does blur the line between the rounds.
The fourth round
The fourth round, originally scheduled from April 1, 2018 through March 31, 2020, is winding down. Only 24 more participated in the primary examination between October 1, 2021 and March 31, 2022, with no change in participation rate of 62.3%. This is still below what the prior rounds registered (81.7% for the first round, 71.0% for the second round, and 64.7% for the third round).
The fourth round, originally scheduled from April 1, 2018 through March 31, 2020, is winding down. Only 24 more participated in the primary examination between October 1, 2021 and March 31, 2022, with no change in participation rate of 62.3%. This is still below what the prior rounds registered (81.7% for the first round, 71.0% for the second round, and 64.7% for the third round).
No one newly received the "B" assessment. Five newly participated in the confirmatory examination with 2 undergoing FNAC (fine-needle aspiration cytology). They, two females, were both diagnosed with suspected thyroid cancer. One, diagnosed between October and December 2021, was age 9 at the time of the 2011 nuclear accident. She is from a FY2018- targeted municipality and resided in Aizu. Her third-round result was A2 nodules. The other one, diagnosed between January and March 2022, was age 14 and resided in Nakadori in 2011. She was never examined prior to the fourth round.
Two (one each from FY 2018 and FY2019 municipalities) were newly confirmed with papillary thyroid cancer after undergoing surgery.
In summary, as of September 30, 2021, the number of suspected or confirmed thyroid cancer cases for the fourth round is 39, of which 34 have been surgically confirmed as papillary thyroid cancer.
The previous results from the third round are as follows: 26 with "A" (6 with A1, 13 with A2 cysts, 6 with A2 nodules, and 1 with A2 cysts and nodules), 9 with "B," and 4 with no prior result.
The fifth round
The fifth round targets 252,902 individuals, excluding about 21,000 born in FY 1996 (April 2, 1996 to April 1, 1997) and about 20,000 born in FY 1997 (April 2, 1997 to April 1, 1998) who are earmarked for the Age 25 Milestone Examination in FY 2021-2022. (It has previously been discussed how this exclusion skews age distribution graphs to the left.)
The COVID-19 restrictions have had a significant impact on the progress of the fifth round which began in April 2020: school closures initially halted the school-based screening, and a burden on medical facilities reduced participation in the confirmatory examination. [Note: The fifth round was originally earmarked for FY 2020-2021 (April 2, 2020 to March 31, 2022), but the pandemic has forced an extension of the screening period by one year as described in this proposal: Elementary and middle school students from FY 2020 municipalities will undergo the TUE in FY 2020-2021, while FY 2021 municipalities will be pushed to FY 2022. For high school students, the TUE will be conducted in FY 2021-2022 with the exception of those who were already examined in FY 2020.]
The sixth round is expected to return to a two-year screening cycle beginning April 2023.
As of March 31, 2022, 74,986 participated in the primary examination, including 29,104 new participants, and its participation rate increased from 18.1% to 29.6%, still quite low. Participation rates by age group increased from 31.3% to 48.1% in ages 8-11, from 20.1% to 36.0% in ages 12-17, and from 7.4% to 10.3% in ages over 18. The primary examination results available nearly doubled to 69,822 (93.1%), and so did the number of "B" assessment to 869 (an additional 411 new cases) which qualifies for the confirmatory examination.
Two hundred seventy-nine newly participated in the confirmatory examination, 15 underwent FNAC, and 5 (all females) were diagnosed with suspected thyroid cancer. One was diagnosed from 5 FNAC participants between October and December 2021, and she is from a FY2021 municipality. Her previous result was A1. Remaining 4 were diagnosed from 10 FNAC participants, and 3 are from FY2020 municipalities and 1 from a FY2021 municipality. Their previous results include 1 with A1 and 3 with A2 cyst.
Age and sex distributions of suspected/confirmed cancer cases for the fifth round are available for the first time, likely because the number of suspected/confirmed cancer cases reached two digits. It shows 3 were ages 5 or younger at the time of the March 2011 nuclear accident: a male at age 2, a female at age 4, and a female at age 5.
Two from FY 2020 municipalities and 1 from a FY2021 municipality have been confirmed with papillary thyroid cancer after undergoing surgery.
In summary, as of March 31, 2022, the number of suspected or confirmed thyroid cancer cases for the fifth round is 11, of which 6 have been surgically confirmed as papillary thyroid cancer.
The previous results from the fourth round are as follows: 8 with "A" (3 with A1, 4 with A2 cysts, 1 with A2 nodules), 2 with "B," and 1 with no prior result.
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 252,902 for the fifth round.
The results reported this time are from the data up to March 31, 2022, and this time some regional data (only for the primary examination) is reported, following the first-time appearance of age and sex distribution graphs for suspected and confirmed cancer cases in the last report. FY1996 cohort began screening this fiscal year (FY2022), and their primary examination results are included this time, but this data is excluded from the secondary examination results at this time due to a limited number of participants. Moreover in FY2022, those born in FY1992 became eligible to participate in the Age 30 Milestone Screening, but no data was reported on this.
Since the previously reported results as of September 30, 2021, target population increased to 108,713 due to an addition of 21,020 born in FY1996. The primary examination participation increased by 1,678 to total participants of 9,841, but the participation rate actually decreased slightly from 9.3% to 9.1% due to a larger denominator from the target population increase.
An additional 90 participants received "B" assessment in the primary examination, and a total of 504 qualified for the confirmatory examination. Seventy-four of 90 participants with newly assessed "B" are from FY1996 who were excluded from the report this time. Thus the confirmatory examination results covered 430 who are eligible, an increase of 16 since the last report. Twenty-five more participated in the confirmatory examination, making the total participants 353, and 345 (39 more than last time) have the final results. After FNAC was conducted in 6 individuals (with total FNAC cases of 31), 3 individuals (all females who were age 15 at exposure) were diagnosed with suspected thyroid cancer. Their prior screening results were 2 with A2 cysts and 1 with no prior screening. Regional data reported for the first time only includes the primary examination data, and no information is available as to residence location information of these cases.
In summary, the number of suspected or confirmed thyroid cancer cases from the Age 25 Milestone Screening increased by 3 to 16. The results from the prior screening are: 4 with "A" (1 with A2 nodules, 3 with A2 cysts), 3 with "B" and 9 with no prior screening.
Four new surgical cases (all papillary thyroid cancer) were added, and the number of surgically confirmed thyroid cancer increased to 10, including 9 papillary thyroid cancers and 1 follicular thyroid cancer.
Note: The FNAC results this time show a minimum tumor diameter of 5.3 mm, which is 0.9 mm smaller than last reported. This means that newly detected tumors are smaller and thus potential candidates for non-surgical active surveillance. Of 16 suspected thyroid cancer cases, 10 have undergone surgery. With the cancer cases being mostly in their late 20's, there is a possibility that remaining 6 are under active surveillance.
Sex ratio
All 10 newly diagnosed with suspected thyroid cancer are females this time. A female to male ratio has increased significantly to 10:1 in the fifth round, and there is a mild increase to 3:1 in the Age 25 Milestone Screening. FMU suggested 3 possible explanations for this increase:
1) Nodules tend to be detected more in females;
2) Progress status of the fifth round up to March 2022 does not include the results of the school-based screening with younger participants in Hamadori and Aizu, which just started in April 2022; and
3) There are more females than males participating in the Age 25 Milestone Screening. The primary examination results by sex in Appendix 4 of the most recent report show nearly twice as many female participants than males (6,233 vs. 3,287). This tendency was already seen in data up to September 2020 (3,884 females vs. 2,023 males) in the latest available English translation of the report from the 41st session.
However, the fifth-round sex ratio is likely to change since it is still progressing.
Expected upcoming 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: 48.1% in ages 8-11, 36.0% in ages 12-17, and 10.3% in ages over 18 in the fifth round, and 9.1% for the Age 25 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.
UNSCEAR2020/2021 Report
UNSCEAR Report 2020/2021 (press release) concluded that future health effects, e.g. cancer directly related to radiation exposure from the 2011 Fukushima Daiichi Nuclear Accident are not likely to be discernible. Main findings of UNSCEAR 2020/2021 were introduced to the Oversight Committee 3 times this year: the 44th session in May, the 19th Subcommittee session in August, and at the 45th session in September during a report on proceedings of the 19th Subcommittee session.
This redundancy is telling and believed to reflect an ulterior motive on the part of the Ministry of the Environment (MOE) which would like to bring "closure" to the matter of radiation exposure. Some committee and subcommittee members take them at face value as words from an authoritative international agency, but some who did not fully agree with the rushed summary of the second-round results (see this post) question validity of the report as well as transparency and integrity of UNSCEAR as an agency.
In particular, attention was drawn to a transfer coefficient of iodine into the thyroid gland, which is set at 30% by ICRP. For the Fukushima report this coefficient was reduced by half to 15% owing to iodine-rich diet of the Japanese population, and consequently doses would be reduced in half. Members of the public and experts have questioned how reasonable this reduction is since modern Japanese diet is not always rich in iodine.
The very question was raised at the 45th session by a committee member Sakae Shibusawa of Tokyo University of Agriculture and Technology. It is a known fact that Subcommittee Chair Gen Suzuki leads a research team on the reconstruction of early internal doses funded by the MOE, and his team's work that reduced thyroid equivalent dose estimates (published paper, 2018 MOE report) contributed to updated dose estimates by UNSCEAR. Suzuki said that his team determined a thyroid accumulation rate for the Japanese to be 18.6%, and UNSCEAR determined it to be 15%. Suzuki also stated that thyroid accumulation was not affected so much by the amount of iodine intake but more related to "genetic variations" in transport of iodine into the thyroid gland by NIS (sodium iodine symporter) and renal clearance. If the amount of iodine intake does not matter so much, why emphasize it so much? Furthermore, an assumption that the Japanese dietary habits include iodine-rich foods does not seem to be updated, failing to consider studies on modern dietary habits of the Japanese with lower iodine intake. (Added on September 19, 2022.)
It's astonishing to think someone whose research team is actively contributing to reduced dose estimates is presiding over proceedings of the TUE Subcommittee where a relationship between thyroid cancer and thyroid doses is being investigated. Suzuki has declared that the Subcommittee would not take clinical and pathological data into consideration and focus on epidemiological analyses. When Suzuki was appointed Chair, it was not too hard to imagine what would eventually happen, but what is actually happening is worse than imagined.
It should not be forgotten that the third-round data is still under evaluation, and the Oversight Committee has not come to a definitive conclusion that radiation health effects are unlikely. In truth, it is going to take many years to elucidate a cause of the increase in thyroid cancer in Fukushima, whether it be a true increase due to some factors such as radiation exposure or overdiagnosis.
The rushed summary of the second round raised many questions about transparency of data and credibility of its analysis (see this post). The first round was originally assumed to offer "baseline" data, to which the second round would be compared. Quietly the second round has essentially become part of the baseline in the English papers published by FMU (see this post). ("Quietly" because this is not a common perception at the Oversight Committee or the Subcommittee.) If the third-round data is too small, why not combine it with the second-round data with more thyroid cancer cases than the fourth round? This is unlikely because FMU has done everything to make any sign of dose response disappear so far. (Added on September 19, 2022.)
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, 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, 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, 4 cases previously unexamined
- Fifth round (11 cases): 3 case with A1, 5 cases with A2 (4 cyst and 1 nodule & cyst), 2 cases with B, 1 case previously unexamined
- Age 25 Milestone Screening (16 cases): 4 cases with A2 (1 nodule and 3 cyst), 3 cases with B, 9 cases previously unexamined
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