Research Center for Japanese Electric Power Industry Refutes Application of Radiation Hormesis in Radiation Protection

Below is a translation of the June 13, 2014 statement by the Central Research Institute of Electric Power Industry (CRIEPI).


Our Opinions on Radiation Hormesis Effects
June 13, 2014

Radiation Safety Research Center
Nuclear Technology Research Laboratory
Central Research Institute of Electric Power Industry 

• Currently our center is not conducting research on radiation hormesis.
• Based on the knowledge gained so far, we consider it difficult to generalize the effects of hormesis as the low-dose radiation effects and to incorporate them into the radiation risk assessment.
• There are some instances where merchandise with hormesis effects are sold with reference to our research results, but our center has nothing to do with it.

From the 1990s to the early 2000s, our center conducted studies to verify the effects of radiation hormesis. We elucidated that various hormesis-like effects were induced by low-dose radiation in animal experiments under certain conditions. However, at this time, we consider it difficult to generalize the effects of hormesis as the low-dose radiation effects and incorporate them into the radiation risk assessment mainly for the following two reasons.

First, many of the radiation hormesis effect verification experiments use animals not in healthy conditions (animals born prone to illnesses or animals with cancer cells transplanted). A special series of experiments like these are used to improve observation of the radiation response since the low-dose radiation effects are extremely difficult to detect. We consider it inappropriate to estimate effects in healthy human from the results obtained from such experiments.

Second, verification experiments of the radiation hormesis effects limit indices which are being observed. For instance, in research on diseases caused by reactive oxygen, indices related to reactive oxygen are studied: whereas in most cases, indices considered as issues related to general radiation effects, such as lifetime cancer incidence or lifespan changes, are not studied. As the effects of radiation are multifaceted, we believe they should not be determined only by one-sided data.  

Please keep the above points in mind when viewing past research results of the radiation hormesis effects currently listed on our website. 

Furthermore, although we consider it difficult to apply the low-dose radiation hormesis effects towards the radiation risk assessment of the public, this does not mean we flatly deny their application to medical fields. However, please beware that our center has nothing to do sales of merchandise claiming radiation hormesis effects based on the results of our research (we will never cooperate with sales activities of specific products).

Surgical and Pathological Details of Fukushima Thyroid Cancer Cases Released on August 31, 2015

Below is an English translation of the information released by Fukushima Medical University at the August 31, 2015 meeting of the 20th Oversight Committee for the Fukushima Health Management Survey. It includes surgical and pathological details of the 96 thyroid cancer cases operated on at Fukushima Medical University as of March 31, 2015. (See this post for an English translation of the previous version released on November 11, 2014).

These 96 cancer cases, along with one case post-surgically diagnosed to be a benign nodule and 7 cases operated on at other medical facilities, comprise the 104 cases (99 from the first round and 5 from the second round screening) that had undergone surgeries as of the 19th Oversight Committee Meeting for the Fukushima Health Management Survey held on May 19, 2015. This information is essentially the most updated details of the surgical cases since only one more surgical case (papillary thyroid cancer; age and tumor size unknown) was added as of June 30, 2015 (probably due to the new school year starting in April in Japan), according to the information released at the most recent Oversight Committee meeting held on August 31, 2015. 

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August 31, 2015

Regarding Surgically Indicated Cases


Shinichi Suzuki, M.D., Ph.D.
Chair, Division of Thyroid and Endocrine Surgery
Fukushima Medical University Hospital


As of March 31, 2015, 104 among those eligible for thyroid examination underwent surgery after being diagnosed to have “malignant or suspicious” tumors in the confirmatory examination. 97 cases were operated on at the Division of Thyroid and Endocrine Surgery, Fukushima Medical University and 7 at other facilities. As 1 of 97 cases turned out to be a benign nodule post-operatively, 96 thyroid cancer cases are discussed here. According to the pathological evaluation, 93 cases were papillary thyroid cancer and 3 were poorly differentiated thyroid cancer.

In the pre-operative diagnosis, tumor diameter was > 10 mm in 63 cases (66%) and and ≤10 mm in 33 (34%). Also, of 33 cases with tumor diameter ≤10 mm, lymph node metastasis, mild extrathyroidal extension, or distant metastasis were suspected in 8 (8%), not suspected (cT1acN0cM0) in 25 (25%). Of these 25 cases, 22 were suspected to be close to the trachea or the recurrent laryngeal nerve, or have mild extracapsular extension. The remaining 3 cases were operated on according to patients’ wishes, despite the recommendation of non-surgical follow-up observation.

Furthermore, 23 (24%) cases were positive for lymph node metastasis, and 2 cases (2%) were suspected of distant metastasis — multiple lung metastasis.

Surgical methods included total thyroidectomy in 6 cases (6%), and hemithyroidectomy in 90 cases (94%). Lymph node dissection was conducted in all cases, with 80% limited to the central compartment and 20% including lateral compartment. As much as possible, small-size incisions of 3 cm were used.

The post-surgical pathological diagnosis revealed 28 cases (29%) with tumor diameter ≤ 10 mm, excluding 14 cases with mild extrathyroidal extension. And 8 cases (8%) had no lymph node metastasis, extrathyroidal extension, or distant metastasis (pT1a pN0 M0). 

Of all 96 cases, mild extrathyroidal extension (pEX1) was seen in 38 cases (39%), and lymph node metastasis was positive in 72 cases (74%). No post-operative complications (post-surgical hemorrhage, permanent paralysis of recurrent laryngeal nerve, hypoparathyroidism, or hypothyroidism after hemithyoidectomy) were observed.

Due to a small number of pediatric thyroid cancer cases [in general], a strict comparison is not yet possible. However, in general, juvenile thyroid cancers are characterized by good prognosis despite a higher rate of lymph node metastasis, if appropriately treated. Pediatric thyroid cancers with pre-operative findings of large lymph node metastasis, marked extra thyroidal extension (EX2) and distant metastasis are considered to belong to a high risk group, and total thyroidectomy is recommended even when the cancer is localized to one side of the thyroid gland. However, when lymph node metastasis and mild extrathyroidal extension are not apparent pre-operatively but found in the post-operative pathological diagnosis for the first time, these findings are considered unrelated to the prognosis. Therefore, every case with these findings [i.e. post-surgical lymph node metastasis and mild extrathyroidal extension] does not necessarily have poor prognosis, but it is unclear if the prognosis would still be good without surgery, and these findings do not offer proof of unnecessary surgery. These discussions need to be carried out carefully, and we intend to follow the development of the examination further. Removal of the entire thyroid gland necessitates a continual use of the thyroid hormone medication, but removal of only one half of the thyroid gland preserves the thyroid function from the remaining half, making the thyroid hormone medication unnecessary and allowing patients to lead daily lives just as they did before surgery. Therefore, at FMU we perform hemithyroidectomy unless the case is clearly high risk, in an effort to maintain the quality of life (QOL) of the patients.

Fukushima Thyroid Examination August 2015: 104 Thyroid Cancer Cases Confirmed, 6 in the Second Round Screening

The Twentieth Prefectural Oversight Committee for Fukushima Health Management Survey convened in Fukushima City, Fukushima Prefecture, on Monday, August 31, 2015. This marked the beginning of a new two-year term for the committee members. Most of the committee members carried over, and Dr. Hokuto Hoshi was chosen as the committee chair again. (See this post for details of the Oversight Committee members).

Among other information, the Oversight Committee released the latest results of thyroid examination, consisting of Initial Screening or the first round screening (originally scheduled to be conducted from October 2011 to March 2014, and essentially completed as of April 30, 2015 with some confirmatory examination results pending) and Full-Scale Screening or the second round screening (from April 2014 to March 2016). It has been a little over 3 months since the last committee meeting on May 19, 2015, and the latest results include 3 more months worth of data confirmed as of June 30, 2015.

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.

As of June 30, 2015, there are 11 more (1 from the first round and 10 from the second round) malignant or suspicious cases, for a total of 137 (138 including the single case of post-surgically confirmed benign nodule). The number of surgically confirmed cancer cases, excluding the case of benign nodule, now totals 104 (98 from the first round and 6 from the second-round), and the remaining 32 more await surgical confirmation. Since the last results were released, only 1 case has been operated on. This may be due to the patients scheduling surgeries during school breaks.

Initial Screening (the first round screening) 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. 

Full-Scale Screening (the second round screening), to be conducted every 2 years until age 20 and every 5 years after age 20, additionally targets those who were born in the first year after the accident, aiming to examine approximately 385,000 individuals in a 2-year period.  

A female from Iwaki City, age 16 at the time of the March 2011 accident (i.e. at exposure), was the newly diagnosed suspicious/malignant case from the first round. Confirmatory examination from the first round has 48 cases with pending results. It is possible there may be more suspicious/malignant cases from these 48 cases.

In the second round, 10 cases were newly diagnosed to be malignant/suspicious including 5 males (age at exposure: 10, 14, 15, 17 and 18) and 5 females (age at exposure: 9,11,13,13,13). Their places of residence at exposure include 7 municipalities: FY 2011 target municipalities such as Namie Town, Minamisoma City, and Date City (3 cases); and FY 2012 target municipalities such as Fukushima City (2 cases), Motomiya City, Koriyama City, and Kori Town. 

Of the 25 suspicious/malignant cases in the second round, 10 were A1, 13 were A2, and 2 were B in the first round. (Of the newly diagnosed 10 cases, 2 were A1, 7 were A2, and 1 was B in the first round). Dr. Kazuo Shimizu, a thyroid surgeon and one of the committee members, was concerned whether these 10 A1 and 13 A2 cases might have had lesions which were missed (i.e. missed diagnosis) in the first round. If they weren't missed diagnoses, that means either the first round lesions became cancerous or cancer appeared newly since the first round. In the previously A1 cases, cancer most likely appeared newly as by definition A1 had no ultrasound findings. The question is how many of the 13 A2 cases might have developed new lesions since the last screening: if the A2 diagnosis was for nodules, they could have been precancerous lesions, but cysts are usually not expected to turn cancerous unless there was a solid component within (cysts with solid components are considered nodules in the Fukushima thyroid examination protocol). According to Dr. Akira Otsuru, director of the thyroid ultrasound examination, none of the cases had missed diagnoses in the first round, and 2 of the 13 A2 cases were nodules, with the remaining 11 being cysts. This means 21 (10 A1 and 11 A2 with cysts) cases had new suspicious/malignant lesions develop in the last 2-3 years since the first round screening.

As for the 2 cases which previously were diagnosed with B assessment, Dr. Otsuru would not answer, citing protection of patient privacy, whether they underwent the fine-needle aspiration biopsy/cytology in the first round.

In regards to the information sheet called Regarding Surgically Indicated Cases (for an English translation, see this post; the previous version can be seen here) submitted by Dr. Shinichi Suzuki, a thyroid surgeon at Fukushima Medical University and former director of thyroid ultrasound examination, a question was raised during the press conference as to whether the suspicious/malignant cases were overdiagnosed and/or overtreated. Dr. Kazuo Shimzu said that he felt that the fact 39% had extrathyroidal extension (pEX1 by the Japanese thyroid cancer diagnostic classification guideline; equivalent to T3) and only 8% showed no lymph node metastasis meant surgeries were conducted appropriately.

Fukushima Prefecture officials introduced a medical expense reimbursement program and a research study plan on the effect of radiation exposure, organized by the prefecture and commissioned to Fukushima Medical University.

The medical expense reimbursement program was implemented in order to cover out-of-pocket expenses for the residents who were diagnosed, as a result of the confirmatory examination, with thyroid cancer or other thyroid conditions requiring regular medical follow-up. Unlike the ultrasound screening examination which bears no cost to the participants, the treatment (clinical) phase of the thyroid examination shifts to regular medical care using the national health insurance system, incurring a copay of 20-30%. Fukushima residents 18 or younger (or more accurately, until March 31 once they turn 18) receive free medical care covering the copay, but in the beginning of a new fiscal year after they turn 18, they will be responsible for the 30% copay. As 63 of 112 suspicious/malignant cases in the first round are 18 or older at diagnosis, the undue financial burden on them and their families has been an issue. The Fukushima Prefectural assembly has approved the medical expense reimbursement program to offer a financial relief to the 900-1000 eligible residents. (Note: This does not mean the prefecture expects all of these 900-1000 residents to get cancer as it was speculated when the news first came out with incomplete details. Some have conditions/lesion -- no specifics released -- which happened to have been discovered during the screening).

A research project currently being considered is on the estimation of the expected number of suspicious/malignant cases in Initial Screening from a model of thyroid tumor progression based on the national incidence data on thyroid cancer. The project team will include Fukushima Medical University, Osaka University, Nagoya University, and Radiation Effect Research Foundation, and the findings will be written up and promptly reported to the Oversight Committee.

It appears that the Fukushima Prefectural government is trying to take control of how the Fukushima Health Management Survey data is used, as Fukushima Medical University stays busy publishing a multitude of studies based on the data while failing to disclose relevant information in a transparent manner. 

There was also a suggestion from a committee member, Dr. Fumiko Kasuga from National Institute of Health Sciences, to replace the often used phrase, "XX is unlikely to be due to the effect of radiation exposure" with something like, "A small possibility cannot be denied that XX is due to the effect of radiation exposure."

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A summary of the results are provided below for Initial Screening and Full-Scale Screening, followed by unofficial translation of selective tables from the results. All numbers shown below are from the data analysis as of June 30, 2015.

Initial Screening (October 2011 - April 2015)

Total number targeted: 367,685
Number of participants in primary examination: 300,476
Number with confirmed results: 300,476

• A1   154,606 (51.5%) (no nodules or cysts found)
• A2   143,576 (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: 2,108

Number with confirmed results : 2,056

Number of fine-needle aspiration cytology (FNAC): 537

Number suspicious or confirmed of malignancy: 113 (including one case of benign nodules)

Number with confirmed tissue diagnosis after surgery: 99

• 1 benign nodule
• 95 papillary thyroid cancer
• 3 poorly differentiated cancer

Full-Scale Screening (April 2014 - March 2016)

Total number targeted: 378,778

Number of participants in primary examination: 169,455

Number with confirmed results: 153,677

• A1   63,884 (41.6%) (no nodules or cysts found)
• A2   88,570 (57.6%) (nodules ≦ 5.0 mm or cysts ≦ 20.0 mm)
• B       1,223   (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: 1,223

Number of participants in confirmatory examination: 767

Number with confirmed results: 669

Number of FNAB: 88

Number suspicious or confirmed of malignancy: 25

Number with confirmed tissue diagnosis after surgery: 6

• 6 papillary thyroid cancer

Unofficial translation of selected tables

Initial Screening

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 June 30, 2015

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 June 30, 2015

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

Full-Scale Screening

Table 1. Primary examination coverage as of June 30, 2015

Table 2. Number and proportion of children with nodules/cysts as of June 30, 2015

Table 4. Changes in the results of Initial Screening and Full-Scale Thyroid Screening Program

Table 5. Confirmatory testing coverage and results as of June 30, 2015 

Table 6. Cytology results (including information from Appendix 6: Surgical cases of suspicious or malignant cases)