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.)
- 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,
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.
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.
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.
- 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 (36 cases): 8 case 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