Fukushima Thyroid Examination June 2016: 57 Cases Suspicious or Confirmed of Thyroid Cancer in the Second Round Screening

131 Thyroid cancer cases confirmed in Fukushima as of March 31, 2016--101 in the first round and 30 in the second round (Total of 172 cases including suspected cancer cases--115 in the first round and 57 in the second round).


The 23rd Prefectural Oversight Committee for Fukushima Health Management Survey convened in Fukushima City, Fukushima Prefecture, on Monday, June 6, 2016. 

Among other information, the Oversight Committee released the latest results (March 31, 2016) of the Full-Scale thyroid examination, or the second round screening, which was conducted over a two-year period from April 2014 to March 2016. The second round screening is essentially ongoing in terms of the confirmatory examination, so the results are not complete.

For the Initial (Preliminary Baseline) Screening, or the first round screening, the updated, corrected version of the results was released. 

There has been no updated information on clinicopathological details of the surgical cases since August 2015 that showed 74% lymph node metastases post-surgically. The most recent publication in Thyroid by Fukushima Medical University covering the first round screening results as of the August 2015 report only includes older information from the November 11, 2014 Thyroid Examination Evaluation Subcommittee meeting available here.

An official English translation of the results is available here. The narrative below contains some information gathered from the live webcast of the Oversight Committee meeting and the subsequent press conference. 

Overview
As of March 31, 2016, there are 6 more cases with malignancy or suspicion of malignancy from the second round, for a total of 172 (173 including the single case of post-surgically confirmed benign nodule). The number of surgically confirmed cancer cases, excluding the aforementioned case of benign nodule, now totals 131 (101 from the first round and 30 from the second round), and the remaining 41 (14 from the first round and 27 from the second round) await surgical confirmation. Since the last results were released, 14 additional cases from the second round have been operated on and confirmed as papillary thyroid cancer by post-surgical pathological examination of the resected thyroid gland tissue.

For the first time, there was a case of age 5 (male) at the time of the accident. This did not get a special mention during the committee meeting, but various domestic and international experts have used the absence of age 5 or younger at exposure as one of the reasons why Fukushima cancer cases were unlikely to be related to radiation exposure. There were a few questions during the press conference regarding how the committee perceived this particular case. The answer was evasive: the single case of age 5 at exposure would not mean much, especially without the exposure dose information.

Initial (Preliminary Baseline) Screening (a.k.a. the first round)
The first round targeted about 368,000 individuals who were age 18 or younger, residing in Fukushima Prefecture at the time of the Tokyo Electric Fukushima Daiichi nuclear power plant accident on March 11, 2011. There were 300,476 actual participants in the primary examination, giving rise to the participation rate of 81.7%. As of March 31, 2016, there are 116 cases with malignancy or suspicion of malignancy, including a case of the post-surgically diagnosed benign nodule: 102 underwent surgery and 101 were confirmed with thyroid cancer (100 papillary thyroid cancer and 1 poorly differentiated thyroid cancer). 

An additional, updated information from the first round
Details of the three cases orally presented previously were revealed: 2 females (ages 13 and 18) and 1 male (age 17) with their municipalities of residence including Yabuki Town, Hanawa Town, and Aizumisato Town, all FY2013 target municipalities.

There are about 160 who did not participate in the confirmatory examination, but about 60 went through the second round examination and have been reclassified as the A assessment.

Another notable update for the first round was the number of poorly differentiated thyroid cancer, which was decreased from 3 to 1 in accordance with the November 2015 revision of Japan's unique thyroid cancer diagnostic guidelines. No specific details were given regarding the reclassification of 2 (1 each from FY2011 and FY2012) of the 3 cases of poorly differentiated thyroid cancer as papillary thyroid cancer. According to some of the abstracts from the Japan Association of Breast and Thyroid Sonology meeting in late May 2016, it seems that according to the previous guidelines, poorly differentiated thyroid cancer was diagnosed if there was even a small portion of tumor showing poorly differentiated features, whereas the new guidelines requires poorly differentiated features to compose more than 50% of the tumor.

Full-Scale Screening (a.k.a. the second round)
To be conducted every 2 years until age 20 and every 5 years after age 20, the second round screening additionally targets those who were born in the first year after the accident, eventually aiming to examine 381,286 individuals in a 2-year period. As of March 31, 2016, 267,769 have participated in the primary examination of the second round at the participation rate of 70.2%. 256,670 have received confirmed results of the primary examination, and 2,061 turned out to be eligible for the confirmatory examination. 

The confirmatory examination is only two-thirds completed. Of 1,345 who actually underwent the confirmatory examination, 1,242 received confirmed results including 169 that underwent fine-needle aspiration cytology (FNAC). 57 cases had FNAC results suspicious for cancer. Confirmation of thyroid cancer requires pathological examination of the resected thyroid tissue obtained during surgery. As of March 31, 2016, 30 underwent surgery and all 30 were confirmed to have papillary thyroid cancer.

Newly diagnosed cases in the second round
In the second round, 6 cases were newly diagnosed by FNAC to be malignant or suspicious of malignancy. There were 4 males (age at exposure: 5, 8, 14 and 15) and 2 females (age at exposure: 10 and 15). Their places of residence at exposure include 4 municipalities: FY 2014 target municipalities such as Okuma Town and Koriyama City (2 cases); and FY 2015 target municipalities such as Iwaki City (2 cases) and Kagamiishi Town. (In the first round, Okuma Town was included in the FY 2011 target municipalities; Koriyama City in the FY 2012 target municipalities; and Iwaki City and Kagamiishi Town in the FY 2013 target municipalities). 

Cytology results show the 5-year-old (age at exposure) to be from FY2015 screening. His municipality is deduced to be Iwaki City based on the confirmatory examination implementation status by municipality (not translated in this post). Of 44,143 Iwaki City residents who participated in the second round screening, 322 were eligible for the confirmatory examination. Only 105 have actually participated in the confirmatory examination as of March 31, 2016, and 74 of them have confirmed results. Thus, more confirmatory examination results are expected from Iwaki City, the largest of the FY2015 target municipalities. 

Prior diagnostic status of the cases newly diagnosed in the second round
Of 57 total cases with malignancy or suspicion of malignancy in the second round, 28 were A1, 25 were A2, and 4 were B in the first round. (In the 6 cases with malignancy or suspicion of malignancy reported this time, 3 each were classified as A1 and A2 in the first round). 

28 cases that were A1 in the first round screened suspicious for malignancy in the second round. This would appear to be a new onset after the first round since A1 cases by definition have no ultrasound findings of cysts or nodules.

In 25 cases that were A2 in the first round, it is not clear how many were cysts, but 15 of 22 were cysts in the last report. Thus the majority of the second round cases appeared to have developed thyroid cancer in 2 to 3 years since the first round.


First Round or Initial Screening (October 2011 - April 2015)

Total number targeted: 367,672
Number of participants in primary examination: 300,476
Number with confirmed results: 300,476

• A1   154,607 (51.5%) (no nodules or cysts found)
• A2   143,575 (47.8%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
• B        2,293   (0.8%) (nodules ≧ 5.1 mm or cysts ≧ 20.1 mm)
• C               1   (0.0%) (requiring immediate secondary examination)

(Note: Cysts with solid components are treated as nodules).

Number eligible for confirmatory (secondary) examination: 2,294

Number of participants in confirmatory (secondary) examination: 2,128

Number with confirmed results : 2,086

Number of fine-needle aspiration cytology (FNAC): 545

Number suspicious or confirmed of malignancy: 116 (including one case of benign nodules)

Number with confirmed tissue diagnosis after surgery: 102

• 1 benign nodule
• 100 papillary thyroid cancer
• 1 poorly differentiated cancer

Second Round or Full-Scale Screening (April 2014 - March 2016)

Total number targeted: 381,286

Number of participants in primary examination: 267,769

Number with confirmed results: 256,670

• A1   102,870 (40.1%) (no nodules or cysts found)
• A2   151,739 (59.1%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
• B        2,061   (0.8%) (nodules ≧ 5.1 mm or cysts ≧ 20.1 mm)
• C              0   (0.0%) (requiring immediate secondary examination)

(Note: Cysts with solid components are treated as nodules).

Number eligible for confirmatory (secondary) examination: 2,061

Number of participants in confirmatory examination: 1,345

Number with confirmed results: 1,242

Number of FNAB: 169

Number of cases with malignancy or suspicion of malignancy: 57

Number with confirmed tissue diagnosis after surgery: 30

• 30 papillary thyroid cancer

Unofficial translation of selected tables

Full-Scale Screening

Table 1. Primary examination coverage as of March 31, 2016

Table 2. Number and proportion of children with nodules/cysts as of March 31, 2016

Table 3. Participation rates by age group as of March 31, 2016

Table 4. Comparison with the Initial (Preliminary Baseline) Screening as of March 31, 2016

Note 1: Top line refers to the results of the Preliminary Baseline Screening for confirmed results of the Full-Scale Screening.
            It is not the breakdown of the total Preliminary Baseline Screening results, 300,476.
Note 2: Top line refers to the breakdown of the Full-Scale Screening results in a given category of the Preliminary Baseline Screening results. 

            Bottom line shows the proportion in %.

Table 5. Confirmatory testing coverage and results as of March 31, 2016

Table 6. Cytology results (including information from Appendix 6: Number of surgeries among cases with malignancy or suspicion of malignancy) as of March 31, 2016

Figure 3. Distribution of cases with malignancy or suspicion of malignancy by age (as of March 11, 2011) and sex (females in white and males in gray)

Figure 5.  Estimated external effective doses of those who submitted basic survey questionnaire as of March 31, 2016 (females in white and males in blue) 

Initial (Preliminary Baseline) Screening
(updated information marked with yellow highlights)

Table 1. Primary examination results (final results from October 9, 2011 to April 30, 2015)

Table 2. Number and proportion of children with nodules/cysts

Table 3. Confirmatory testing coverage and results as of March 31, 2016

Table 4. Cytology results (including information from Appendix 7: Surgical cases of suspicious or malignant cases) 

Table 9. Proportion of B or C test results, and suspicious or malignant cases                   As of March 31, 2016

Note 10: Excluding duplicates.

Note 11: Excluding unconfirmed results. 

Note 12: The number of FNAC, out of (c), including those who were reclassified as A1 or A2.

Note 13: Excluding one suspected case found benign after surgery.

Note 14: Tamura City, Minamisoma City, Date City, Kawamata Town, Hirono Town, Naraha Town, Tomioka Town, Kawauchi Village, Okuma Town, Futaba Town, Namie Town, Katsurao Village and Iitate Village

Note 15: Fukushima City, Koriyama city, Shirakawa City, Sukagawa City, Nihonmatsu City, Motomiya City, Koori Town, Kunimi Town, Otamamura Village, Kagamiishi Town, Tenei Village, Nishigou Village, Izumizaki Village, Nakajima Village, Yabuki Town, Tanagura Town, Yamatsuri Town, Hanawa Town, Samegawa Village, Ishikawa Town, Tamakawa Village, Hirata Village, Asakawa Town, Furudono Town, Miharu Town, and Ono Town

Note 16: Iwaki City, Soma City, Shinchi Town

Note 17: Aizuwakamatsu City, Kitakata City, Shimogo Town, Hinoemata Village, Tadami Town, Minamiaizu Town, Kitashiobara Village, Nishiaizu Town, Bandai Town, Inawashiro Town, Aizubange Town, Yugawa Village, Yanaizu Town, Mishima Town, Showa Village, and Aizumisato Town