Issue to be considered #1:
Pediatric thyroid cancer occurrence in Fukushima children is said to be “several tens of times larger.” Larger than what, and how is it calculated?
How one epidemiologist explains
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Dr. Shoichiro Tsugane, an epidemiologist from National Cancer Center and a member of the Oversight Committee
for the Fukushima Health Management Survey as well as the Thyroid Examination Assessment Subcommittee.
(Photo credit: Oshidori Ken) |
“The number of cancer cases shown in the examination results is several tens of times larger than the number of prevalent cases estimated from population-based statistical data such as incidence statistics of thyroid cancer included in the regional cancer registry in Japan. ”
This is a phrase excerpted from the Interim Report submitted by the Thyroid Examination Assessment Subcommittee (referred to as the Subcommittee hereafter) to the 19th Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey (referred to as the Oversight Committee hereafter) on May 28, 2015.
This expression, “several tens of times larger” was not included in the Draft Interim Summary discussed during the 6th session of the Subcommittee held on March 24, 2015. I have attended numerous committee meetings ever since the accident, but this was the first time such a statement as “The number of pediatric thyroid cancer cases in Fukushima Prefecture is large.” appeared in a public document.
“The examination results” mentioned in the Interim Summary refers to the results of the Initial Screening of Thyroid Ultrasound Examination being conducted in children in Fukushima Prefecture since the nuclear accident. Thyroid Ultrasound Examination, covering Fukushima residents who were age 18 or younger as of March 11, 2011, is to be conducted every 2 years up to age 20 and every 5 years after age 20. Initial Screening is the first round of this examination.
Of the eligible 370,000 residents, about 300,000 have confirmed results after the completion of the first round screening. So far 112 children were diagnosed with “confirmed or suspicious” thyroid cancer. What is considered “several tens of times larger” is this number 112, the number of confirmed or suspicious thyroid cancer cases.
Comparison with the pre-accident data
What is “several tens of times larger” compared with, and how is it calculated? I interviewed Dr. Shoichiro Tsugane, one of the Subcommittee members. Dr. Tsugane is an epidemiologist and director of of Research Center for Cancer Prevention and Screening at the National Cancer Center.
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Dr. Tsugane, an epidemiologist and director of of Research Center for Cancer Prevention and Screening at the National Cancer Center.
(Photo credit: Oshidori Ken) |
In this document, Dr. Tsugane estimated, from the 2001-2010 cancer incidence, that the number of prevalent cases of thyroid cancer in ages 18 or younger as of 2010 in Fukushima Prefecture was 2.1. As the participation rate of the pediatric thyroid examination which began in 2011 is about 80%, it is necessary to calculate the number of prevalent cases in the population to be about 80% of the estimate. Therefore, the number to be compared with the result of Initial Screening is 1.7, which is 80% of the number of prevalent cases, 2.1, estimated as of 2010.
Dr. Tsugane calculated that if all 104 cases “confirmed or suspicious of malignancy” (as of the 16th Oversight Committee held on August 24, 2014, including the results up to June 30, 2014) during the post-accident thyroid examination actually turned out to be cancer, these 104 cases would be 61 times the estimated number of prevalent cases as of 2010. Strictly speaking, “several tens of times” refers to this number, 61 times. However, Dr. Tsugane explains, “Initial Screening is not finished yet, and the nature of statistics makes this no more than just an estimation. That’s why I chose to use the expression, ‘several tens of times’ rather than the actual number.”
Incidentally, if all 112* (see clarification below) cases “confirmed or suspicious of thyroid cancer” as of March 2015 actually turned out to be cancer, this number would be 66 times. If all 127 cases, including an additional 15 cases newly diagnosed during the Full-Scale Screening, actually prove to be cancer, the magnification would be 75 times. Moreover, as the aforementioned number (of thyroid cancer cases as of 2010) “1.7” is an estimate, a slight change in this estimation could make the magnification smaller, such as 25 times or 30 times. This is why he “chose to use the expression, several tens of times.”
(*Clarification by translator: Initial Screening was supposed to complete by the end of March 2014, but confirmatory examination is still ongoing and some are still accepted to undergo primary examination as long as they haven’t received notifications for Full-Scale Screening. This is why the number of “confirmed or suspicious” cases has been increasing at each Oversight Committee meeting where the new results are announced).
Dr. Tsugane, as an epidemiological expert, says the large size of this magnification “is not explainable solely by screening effect (i.e. cancer that might be found at later time was detected early due to mass screening).” He continues, “Screening effect has already been studied and written about numerous times, and it is true that diagnosis rate of cancer increases in mass screening. However, the added effect of screening cannot result in so many cancer cases. Some increase may be attributed to screening effect, but it is more practical to interpret there must be other reasons for the increase.”
If the increase is not solely due to screening effect, why is it “several tens of times larger”? Dr. Tsugane says, “It is due to either excess occurrence based on some factors, or diagnosis of many cases of cancer that might not be clinically diagnosed or cause death in the future (i.e. overdiagnosis).” He continues, “I personally think it’s the latter… Nevertheless, it is a fact that we have pediatric thyroid cancer cases which are several times larger than expected.”
For reference, overdiagnosis refers to diagnosis of disease that does not require medical treatment, as opposed to screening effect which means early detection of asymptomatic disease that patients are unaware of, and which eventually requires medical treatment.
Is occurrence “several tens of times larger” than expected due to overdiagnosis?
Is it really overdiagnosis that is going on? I asked Dr. Kazuo Shimizu, chair of the Thyroid Examination Assessment Subcommittee and former chair of the board of the Japanese Society of Thyroid Surgery.
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Dr. Kazuo Shimizu, a thyroid surgeon and Honorary Director Kanaji Hospital, and Professor Emeritus at Nippon Medical School.
Dr. Shimizu is a member of the Oversight Committee for the Fukushima Health Management Survey and chair of the Thyroid Examination Assessment Subcommittee.
(Photo credit: Oshidori Ken) |
“I am not in a position to be able to say, ‘It is not due to overdiagnosis.’ As chair of the Subcommittee, I cannot validate opinions of either side. It is hard for me. I would have been able to voice my opinions more clearly if I hadn’t been elected chair of the Subcommittee.”
Dr. Shimizu, answering my questions between patients at the hospital, did not give me a clear answer. However, physicians actually involved with diagnosis during the thyroid examination unanimously agree that “it is not overdiagnosis.” These physicians include Dr. Akira Miyauchi from Kuma Hospital, one of nation’s top thyroid clinicians, as well as Dr. Shinichi Suzuki from Fukushima Medical University, director of thyroid examination in Fukushima Prefecture.
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Issue to be considered #2:
Up to now, many experts have insisted diagnosis of pediatric thyroid cancer in Fukushima was due to screening effect. However, some physicians are beginning to doubt it. What is happening now?
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Dr. Akira Miyauchi from Kuma Hospital, one of the most experienced thyroid surgeons in Japan,
speaks at the August 5, 2014 Expert Meeting. (Photo credit: Oshidori Ken) |
On August 5, 2014, Dr. Miyauchi made the following statement during the 9th Session of the Expert Meeting Regarding the Status of Health Management of Residents Following the Tokyo Electric Fukushima Daiichi Nuclear Power Plant Accident.
“(…)I am also a member of the Diagnostic Criteria Inquiry Subcommittee of the Thyroid Examination Expert Committee. In fact, I just attended the Subcommittee meeting the day before yesterday where information about the surgical cases at Fukushima Medical University was presented. We were told over 70% of the cases at least had conditions which would ordinarily be considered surgical indications, based on our current standard of care, such as tumor size over 1 cm, presence of lymph node metastases, or some aggressive cases with distant metastases. Remaining 30% or so was smaller than 10 mm in size, but they are what we consider high risk lesions, for reasons such as being near the recurrent laryngeal nerve or the trachea.” When the tumor is near the trachea or the recurrent laryngeal nerve, surgery becomes difficult when the tumor size increases. Furthermore, extension of cancer cells beyond the thyroid capsule begins to affect the surrounding tissues. In these cases, surgery is indicated.
At this Expert Meeting, Dr. Miyauchi talked about how his own hospital handles thyroid cancer: “We have been conducting non-surgical follow-up for small thyroid cancers in the last 21 years. Non-surgical observational follow-up might be appropriate for the low risk thyroid microcarcinoma.”
In 2012, I actually went to interview Dr. Miyauchi at Kuma Hospital in Kobe, and I recall him saying, “Many physicians resect thyroid cancer unnecessarily. They examine patients and operate on them aggressively. The biggest harm of the nuclear accident might turn out to be such excessive surgery.”
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| Oshidori Mako interviews Dr. Akira Miyauchi on February 27, 2012. (Photo credit: Oshidori Ken) |
However, even Dr. Miyauchi, who recommends observational follow-up of thyroid microcarcinoma, says, “Surgical cases in Fukushima’s thyroid examination are what we consider high risk cases, and surgeries are appropriate.” In other words, Dr. Miyauchi denies those cases constitute overdiagnosis.
Regarding the surgeries on pediatric thyroid cancer cases in post-accident Fukushima, Dr. Shinichi Suzuki from Fukushima Medical University discussed the details at the 4th session of the Thyroid Examination Assessment Subcommittee held on November 11, 2014.
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Dr. Shinichi Suzuki, a thyroid surgeon at Fukushima Medical University.
(Photo credit: Oshidori Ken) |
According to Dr. Suzuki, surgeries were conducted on 55 cases of pediatric thyroid cancer at Fukushima Medical University post-accident up to June 30, 2014. One of 55 cases turned out to be a benign nodule after surgery. Remaining 54 consisted of 52 cases of papillary cancer, and 2 cases of poorly differentiated thyroid cancer. (According to the Clinical Management Guideline or CMG, poorly differentiated cancer is more aggressive than differentiated cancer because of the faster progression due to the faster speed of cancer cell division).
In regards to tumor diameter, 42 cases had larger tumor diameter over 10 mm, and 12 cases relatively smaller tumor diameter of 10 mm or below (as per CMG, surgery is indicated for tumors with larger diameter). Of the 12 cases with smaller tumor diameter, 3 cases were suspicious for lymph node or distant metastasis (as per CMG, surgery is indicated for smaller tumors suspicious for metastasis). Of 9 cases with tumor diameter of 10 mm or smaller and no suspicion of metastasis, 7 cases were either adjacent to the trachea or the recurrent laryngeal nerve, or suspicious for extra-capsular extension (as per CMG, surgery is indicated when the tumor is near the trachea or the recurrent laryngeal nerve as surgery becomes difficult when the tumor gets bigger, or when there is extra-capsular extension which affects the surrounding tissues). The remaining 2 cases were operated on due to the wishes of the patients despite the recommendation of observational follow-up.
Furthermore, of 54 cases that underwent surgery at Fukushima Medical University, 17 had lymph node metastasis, and 2 had distant metastasis with suspicion of multiple lung metastasis. (Thyroid cancer is supposed to progress slowly, but in these cases the progression might have been faster due to young age). Surgical methods included total thyroidectomy in 5 cases and hemithyroidectomy in 49 cases. Total thyroidectomy involving the removal of the entire thyroid gland necessitates lifelong dependence on thyroid hormone medication.
In essence, Dr. Suzuki explained that “surgery was indicated and there was no overdiagnosis” in regards to tumors with large diameter, suspicion for metastasis, or proximity to the trachea or the nerve.
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Dr. Shunichi Yamashita (left), former Oversight Committee chair, and Dr. Shinichi Suzuki (right) at the
February 13, 2013 Oversight Committee press conference. This was the last appearance for Dr. Yamashita as chair.
Dr.Suzuki no longer appears at the Oversight Committee meeting to explain the results of
the Thyroid Examination, since he left the position as director of the Thyroid Examination in May 2015,
in order to focus on conducting surgeries and training other surgeons.
(Photo credit: Oshidori Ken) |
A clinician’s opinion
When I asked Dr. Shimizu regarding Dr. Suzuki’s explanation, he said, “I think Dr. Suzuki’s explanation is reasonable as it is the observation of a specialist actually operating on these patients. I also think the opinion of Dr. Miyauchi, the top surgeon from the Japan Society of Thyroid Surgery, is right.”
Dr. Shimizu repeats, however, “I would have had more opportunities to voice my own opinions if I hadn’t been chair of the Thyroid Examination Assessment Subcommittee. But since I am in a position to oversee different arguments, I am not at liberty to say an opinion from a particular side is reasonable.”
I felt that something might be swaying inside Dr. Shimizu.
There was only one occasion during the Subcommittee session where Dr. Shimizu voiced his opinion strongly. It was the 2nd session of the Subcommittee held on March 2, 2014.
“I realize I am the chair of the Subcommittee, but there is something I would like to say outside my role as chair. It has been 10-plus years since I participated in thyroid screening programs in Chernobyl (Editor’s note: Since 1999, Dr. Shimizu has been to Chernobyl as a volunteer, participating in medical support activities, including thyroid ultrasound screening and surgery), but I would like to describe a patient who had thyroid surgery. It was a girl, age 5 or 6, with a large scar in the neck and a hole for tracheostomy in the middle of the neck. This girl will be able to keep living. But she has no voice, she can’t soak in the bathtub up to her neck, and she can’t enjoy conversations with people. What happened to her is that her recurrent laryngeal nerve was damaged on both sides. I don’t know if it is because the nerves had to be resected along with cancer due to the progression of the cancer, or if the nerves were damaged in surgery as they were not identifiable due to the advanced stage of cancer. All I can say for sure is that if the cancer had been detected earlier, this wouldn’t have happened to her.
It is difficult to decide if screening is beneficial or harmful, and it is hard to decide if a case should be operated on. Not all 1 cm microcarcinomas are equal: they vary depending on whether they are located near the nerve, in contact with the trachea, or buried within the thyroid gland. This means that not all cancers below 1 cm in diameter can be followed with observation: rather they need to be looked at on a case by case basis.
This means you need to observe the location and the growth speed of the tumor or the involvement of lymph nodes in individual patients during the follow-up. In this capacity, I think the screening is important.”
He made this statement when the discussion turned to the actual purpose of the screening during the debate on methods of epidemiological studies in relation to the Fukushima thyroid examination. This was a statement he made not as the chair of the Subcommittee, but as a physician who performed surgeries in Chernobyl.
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| Dr. Shimizu answers Oshidori Mako's questions. (Photo credit: Oshidori Ken) |
I brought up with Dr. Shimizu what I have felt during the ongoing coverage of the Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey and the Thyroid Examination Assessment Subcommittee.
Mako: “There have been many pediatric thyroid cancer cases in Fukushima after the accident. It has been suggested it was because of screening effect, but the suggestion was denied by an epidemiologist. Then there has been a talk of overdiagnosis, which is denied by physicians directly involved with the patient care. It seems that this discussion never went anywhere during the Subcommittee session.”
Dr. Shimizu: “We clinicians, specializing in diagnosis and treatment, carefully look into individual cases. We differ, on some critical points, from the experts who make decisions based on numbers. Surgeons in particular understand how much of a burden a surgery is on a patient. We must think of the best treatment for the patient, but we cannot avoid doing surgery when needed. The physicians actually involved with medical care of these patients diagnosed with cancer know the best that it wasn’t overdiagnosis--including patients who had surgeries as well as patients under observation.”
I felt like this might be at least part of Dr. Shimizu’s true opinion.
Mako: “If it’s not overdiagnosis, why are there so many cases of pediatric thyroid cancer?”
Dr. Shimizu: “In terms of radiation exposure, exposure dose in Fukushima is allegedly not the level that caused thyroid cancer in Chernobyl. Therefore, at this time, it is unlikely for radiogenic thyroid cancer to occur in Fukushima as it did after the Chernobyl accident.”
Mako: “But the dose assessment in Fukushima is mostly based on estimated doses as there were very little direct measurements. There is a question about whether the current dose assessment is adequate… (dose assessment is evaluation and assessment of radiation dose people were exposed to. It is the basic knowledge in considering causality between exposure and disease).”
Dr. Shimizu: “As dose assessment is not my area of expertise, I can only base my evaluation on data and reports given to me. However, all members of the Subcommittee share the doubt about adequacy of the dose assessment. That’s why the Interim Summary includes a clause regarding continuation of dose assessment studies in the future.”
In the Interim Summary, the Thyroid Examination Assessment Subcommittee reported to Fukushima Prefecture, “The number of cancer cases in the result is several tens of times larger than the estimated number of patients up to 2010. This may be interpreted as the result of either excessive occurrence due to radiation exposure or over-diagnosis. At present it is not possible to conclude whether thyroid cancer cases detected during screening are radiogenic. Information on internal exposure dose from radioactive iodine in the early post-accident period should continue to be investigated.” Dr. Shimizu concluded, “There are many cases of pediatric thyroid cancer. I think we must accept new data candidly and figure out how to deal with it.”
A relationship between radiation exposure and pediatric thyroid cancer has been consistently denied by the Central Government as well as the Prefecture. But the Interim Summary might have brought this subject back to where it started. Some changes were beginning to be noticeable amongst the researchers and physicians following these patients.
Initial Screening was originally implemented in order to establish a base for studying health effects of the Fukushima NPP accident on thyroid gland. But discovery of excess occurrence was, in a way, unexpected.
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Originally, the purpose of Initial Screening was to establish a baseline for studying health effects of the Fukushima nuclear accident on the thyroid gland.
Discovery of excess occurrence during Initial Screening, then, was outside expectation in a sense.
Overturned prediction
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Dr. Shunichi Yamashita, the first chair of the Prefectural Oversight Committee for the Fukushima Health Management Survey,
at the February 13, 2013 Oversight Committee meeting. He resigned from the position in March 2013.
Dr. Yamashita was appointed a radiation health risk management advisor for Fukushima Prefecture immediately after the Fukushima accident.
(Photo credit: Oshidori Ken) |
The first chair of the Prefectural Oversight Committee for the Fukushima Health Management Survey (called the Oversight Committee) was Dr. Shunichi Yamashita, a board member (in charge of international and affiliate institutes) and vice president (in charge of supporting reconstruction of Fukushima) of Nagasaki University as well as vice president of Fukushima Medical University. He was the committee chair from when the Oversight Committee was first established in May 2011 up to the 10th Oversight Committee Meeting held on February 2013.
Dr. Yamashita continues to contribute articles to a subsection called “Regarding thyroid examination in Fukushima Prefecture” on the Great East Japan Earthquake section of the website of Prime Minister of Japan and His Cabinet. In February 2014, he wrote,
“We consider thyroid cancers detected during the pediatric thyroid examination as spontaneous pediatric thyroid cancer (detected with a fixed probability by screening in all areas even outside of Fukushima) which is not directly related to the nuclear accident. Thus we consider them screening effect.”
However, during one of the Oversight Committee meetings—long after Dr. Yamashita left as chair—Dr. Tsugane, an epidemiologist, reported, “It is difficult to explain the current situation, with the number of thyroid cancer cases for ages 18 and under in Fukushima Prefecture exceeding 100, solely on the basis of screening effect.”
Dr. Yamashita also wrote, “This means many cases of cancer in very early stage were detected during Initial Screening during the two and a half years after the accident. Therefore, this occurrence rate cannot be compared with the rate based on the number of surgeries or the number of cases entered into cancer registry.”
Given such claim, Dr. Tsugane has requested the Division of Surveillance, Center for Cancer Control and Information Services at National Cancer Center to calculate the estimated number of pre-accident cases in Fukushima, from incidence rate based on regional cancer registry. And the analysis led to the expression, “several tens of times larger,” mentioned in the "Interim Summary Regarding Thyroid Examination." In essence, the Interim Summary by the Thyroid Examination Assessment Subcommittee overturned the earlier assessment by the Oversight Committee.
The meaning of Initial Screening
When the Chernobyl accident occurred, IAEA (International Atomic Energy Agency) reported that the occurrence of pediatric thyroid cancer in the affected areas began to increase 4-5 years after the accident.
[Editor’s note: IAEA actually did not admit the excess occurrence during the investigation 4-5 years after the accident. However, 8 years after the accident, WHO finally recognized the excess occurrence which began in the fourth post-accident year. Ryuichi Hirokawa, editor of DAYS JAPAN and founder/director of Chernobyl Children's Fund, Japan, covered a symposium in Ukraine three years after the accident where excess occurrence of pediatric thyroid cancer was reported. He also interviewed Belarusian specialists discussing excess occurrence of pediatric thyroid cancer as well as leukemia. However, at the time, such reports were ignored by organizations like IAEA and ICRP (International Commission on Radiation Protection), which insisted there were no health effects. It wasn’t until the eighth post-accident year that excess occurrence became too obvious to be ignored that it was finally acknowledged by these organizations].
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Ryuichi HIrokawa, a photojournalist and DAYS JAPAN editor.
(Photo credit: Oshidori Ken) |
Due to the fact that the Chernobyl pediatric thyroid cancer occurrence began to increase 4-5 years after the accident, it was decided after the Fukushima Daiichi nuclear power plant accident that the first round (Initial Screening) of thyroid examination be completed before the effect of the nuclear accident appeared. This way the result of Initial Screening would be considered baseline without the effect of radiation exposure to compare with the result of Full-Scale Screening, scheduled to begin 4-5 years after the accident. However, 112 (confirmed and suspected) cases of thyroid cancer were diagnosed during Initial Screening which supposedly had no effect of radiation exposure. People began to wonder if 112 was too high a number under the circumstance.
Actually, there was something Dr. Shimizu said additionally, when voicing the aforementioned opinion made outside his role as the subcommittee chair, during the Thyroid Examination Assessment Subcommittee.
“There is a fact that thyroid cancer occurrence began to increase 4 years after the Chernobyl nuclear accident. But did the increase begin
as of the
4th post-accident year after the continuous examination was conducted since immediately after the accident? Or was it that the thyroid cancer cases were already on the increase but only ‘began to be discovered’ as nodules in the
4th post-accident year? Tumors become palpable when they are 1 cm to 1.5 cm in diameter, and it might take 4 years for them to grow to reach a palpable size. Epidemiologists need to play a central role in evaluating the types of examinations conducted in the first 3 years.”
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| Oshidori Mako interviews Dr. Shimizu. (Photo credit: Oshidori Ken) |
In my interview of Dr. Shimizu, I brought up the questions which had been on my mind.
Mako: “If over 100 cases of pediatric thyroid cancer detected as a result of the screening were not the effect of the nuclear accident but rather the pre-existing latent cancer, wouldn’t that be a serious issue?”
Dr. Shimizu: “I think it is a serious issue. So I suggested during the government and prefectural committee meetings that a similar screening be conducted in other prefectures. Not a small scale study like the
2012 three-prefecture (Aomori, Yamanashi, and Nagasaki) study on 4,000-plus children conducted by the Ministry of Environment (i.e. MOE 3-prefecture study), but a study on all residents ages 18 or younger in some non-Fukushima prefecture. If such a study found a similar rate of occurrence, then Fukushima cases would not be related to the nuclear accident, and if it doesn’t, then there is a high likelihood that Fukushima cases may be the effect of radiation exposure. However, my suggestion, although made on several occasions, was turned down each time for reasons such as ‘There is a moral issue with it.’ and ‘There are too many detriments to the subjects.’”
Regarding the results of the MOE 3-prefecture study, Dr. Yamashita says “the frequency of abnormal findings in pediatric thyroids is about the same as in Fukushima Prefecture.” What he means is the proportions of diagnostic criteria (test results)—A1, A2, B and C—were similar, but that is not the point. Even if each diagnostic category showed similar proportions between Fukushima and the MOE 3-prefecture study, what is significant is the percentage of pediatric thyroid cancer cases diagnosed from each diagnostic category. In Fukushima, there are 112 cases confirmed or suspicious of pediatric thyroid cancer amongst children whose test results were B or C in Initial Screening. Full-Scale Screening conducted 2 years later has so far found 14 cases confirmed or suspicious of pediatric thyroid cancer amongst children whose test results were A1 or A2 in Initial Screening. In other words, the fact that Fukushima and other prefectures share similar proportions of each diagnostic category does not verify anything. What needs to be compared is the proportion of the pediatric thyroid cancer cases.
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| Oshidori Mako intently listens to Dr. Shimizu at the June 1, 2015 interview. (Photo credit: Oshidori Ken) |
I asked Dr. Shimizu further questions about situations in other prefectures. I have investigated cases of pediatric thyroid cancer diagnosed in prefectures near Fukushima Prefecture.
Dr. Shimizu: “Yes, I also have heard of such cases in Chiba Prefecture, the north part of Ibaraki Prefecture, and also Iwaki City to Ibaraki’s north… It seems like I hear of such cases occurring in contaminated areas.”
Doesn’t this mean the thyroid examination is necessary outside Fukushima Prefecture?
Dr. Shimizu: “I am not sure about the examination in an entire prefecture, but it might be necessary to conduct the thyroid examination in certain municipalities or cities in contaminated areas.”
Excess occurrence of pediatric thyroid cancer as a result of Initial Screening might be related to the nuclear accident after all, and the thyroid examination outside Fukushima Prefecture might be necessary—that is what a member of the Oversight Committee is saying now. What is the basis of the experts who have kept insisting “there will be no effect of radiation exposure” since immediately after the accident?
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Is screening every two years adequate? Does the cancer progress between screenings?
Progression of Thyroid Cancer
The pediatric thyroid examination is conducted as part of the Fukushima Health Management Survey at a frequency of every 2 years for ages 18 and younger. I have always thought that was a reasonable interval. However, I began to have a second thought about it as the results of Full-Scale Screening, or the second round screening, began to be disclosed.
Pediatric thyroid cancer cases discovered during this examination show fast progression. After the completion of the first round, or Initial Screening, 15 individuals were newly “confirmed or suspicious of malignancy” during Full-Scale Screening conducted 2 years later. Eight of them were diagnosed with the A1 test result during Initial Screening, meaning there were no nodules or cysts observed in the thyroid gland. However, despite having no lesions on ultrasound, they were diagnosed with cancer requiring surgical resection only 2 years later.
Thyroid cancers are ordinarily supposed to have a very slow progression (i.e. growth speed of the tumor). How is it possible for a tumor to become large enough to require surgical resection only 2 years after no such tumor was detected in the thyroid gland?
This is a question often asked by Dr. Shimizu during the Oversight Committee meetings, directed to representatives of Fukushima Medical University (FMU) which is commissioned by Fukushima Prefecture to conduct the Fukushima Health Management Survey FMU’s reply was vague and convoluted: “It’s not as if these lesions were missed during Initial Screening. In addition, once detected, growth speed of the tumor is not that fast.”
In other words, it’s not that lesions were missed, but there were no nodules or cysts observed at all in the thyroid gland during Initial Screening. However, by the time Full-Scale Screening was conducted 2 years later, tumors with average diameter of 1 cm (minimum 5.3 mm, maximum 17.3 mm) have developed, and they were eventually diagnosed to be “confirmed or suspicious of malignancy” with surgical resection considered appropriate. Does this mean the growth speed of the tumor was fast? Nevertheless, FMU explains, “Growth speed of the tumor, once detected, is slow.” A tumor suddenly appears in the thyroid gland which previously showed no lesions, grows fast, but then the growth slows down once detected by ultrasound. Is that possible?
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| Oshidori Mako asks Dr. Shimizu questions. (Photo credit: Oshidori Ken) |
I asked Dr. Shimizu about such possibility, but his answer was, “I don’t have an answer because I didn’t actually examine them.”
I changed my question: “If a tumor grows large enough to be ’confirmed or suspicious of malignancy’ in the thyroid gland which had no lesions observed two years previously, is it reasonable to conduct the screening once every two years?” Dr. Shimizu replied, “Ordinarily, I think screening once every two years should be adequate. It’s because even if cancer is newly diagnosed during a two-year period, it is not likely to be life-threatening or lower post-treatment QOL (quality of life) as long as it is treated. However, I feel it would be reasonable to honor a request by patients for an examination once a year. There is no need for frequent examinations. I think once every year or two is sufficient.” This was the first time I heard him refer to “once a year.”
Of the 15 cases newly diagnosed to be “confirmed or suspicious of malignancy” during Full-Scale Screening, most were diagnosed as A1 during Initial Examination. Is the screening interval of 2 years reasonable? Is a further discussion necessary?
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Issue to be considered #3:
Was the contaminated food under control?
Were there sufficient post-accident exposure studies?
Both epidemiologists and clinicians state in unison, “Dose assessment is not our specialty, so all we can do is to accept the reported assessment.”
I interviewed a dose assessment expert and one of the members of the Oversight Committee for “Fukushima Health Management Survey,” Professor Shinji Tokonami of Hirosaki University.
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Shinji Tokonami, Ph.D., Professor, Institute of Radiation Emergency Medicine, Department of Radiation Physics, Hirosaki University. (Photo credit: Oshidori Ken).
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Mako: “Professor Tokonami, as an expert, do you think the dose assessment after the Fukushima nuclear accident has been adequate?”
“I think it has been inadequate,” replied Professor Tokonami. “There have been hardly any measurements taken of residents’ exposure doses after the nuclear accident. The half-life of iodine 131, which damages thyroid gland, is 8 days, and it cannot be measured later. All you can do is retroactively estimate the dose from fragmented data of iodine remaining in soil and air.”
Mako: “Can we still conduct such retroactive estimation?”
Prof. Tokonami: “Iodine moves around in various ways in the environment. After the accident, the radioactive plume released from the nuclear reactors, including radioactive iodine, dispersed in every direction. I think the individual exposure dose will vary widely depending on where each person was at the time of the accident and whether the person was hit by the radioactive iodine plume.”
Mako: “Investigation by the Oversight Committee mostly had to do with estimation of external exposure dose based on the record of people’s behavior; it lacks the internal exposure dose assessment based on food intake. (During the 2nd Oversight Committee Meeting, Shunichi Yamashita, who was then chair of the Committee, said, “This Committee will mainly deal with external exposure, and internal exposure is only considered peripherally.”) The Basic Survey questionnaire by the Fukushima Health Management Survey asks people to write in a four-month record of their behavior from March 11, 2011 to July 11, 2011. In regards to internal exposure, there is only a section on the last page of the questionnaire to “declare any consumption of produce grown outside on bare soil or water from a private water-supply system,” and the declaration period is only for 20 days—from March 11 to the end of March. Isn’t it necessary to conduct more survey on the internal exposure dose?
Prof. Tokonami: “I heard of occasions where residents were drinking water from the stream. It is possible to estimate the dose from recorded data if we know which private water-supply system was used by making calculations based on the amount of daily water consumption.”
Mako: “Isn’t it necessary to conduct detailed dose assessment at least in children diagnosed “confirmed or suspicious of malignancy”?
Prof. Tokonami: “We can’t conduct any direct measurements now. What we could do is repeat dose reconstruction from answers on behavior questionnaire of the thyroid cancer patients as well as from some scattered data available.”
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| Oshidori Mako interviews Prof. Tokonami. (Photo credit: Oshidori Ken) |
Contamination of food and contaminated drinking water at evacuation centers
I learned through my investigation that contaminated vegetables, especially leafy vegetables, were in distribution after the 2011 nuclear accident. The government explains, “No contaminated food was distributed. Everything was under control.” However, when I visited the labs and research institutes which actually analyzed commercially distributed foodstuff, they said, “Some vegetables were loaded with iodine,” showing me various measurement data. Of course, this doesn’t mean every foodstuff was contaminated. Suspension and restriction of shipments of contaminated foods was working to some extent. However, some contaminated foods would occasionally slip by into distribution. Some researchers called it, “a bomb vegetable.”
In reality, the provisional regulation values for food was established on March 17, 2011, in response to the nuclear accident. Then, on March 19, 1,510 Bq/kg of iodine 131 was detected in milk from Kawamata Town, Fukushima Prefecture, and the Ministry of Health, Welfare and Labour (MHWL) sent out a request to ban its sale. Also on
March 19, 15,020 Bq/kg of iodine 131 was detected in spinach from Takahagi City, Ibaraki Prefecture, and 14,500 Bq/kg of iodine 131 in spinach in Hitachi City, Ibaraki Prefecture.
But the
MHLW website simply states, “We were contacted by Ibaraki Prefecture regarding the press release shown below.” and there were no special measures actually taken by MHWL itself. Takahagi City and Hitachi City are in Ibaraki Prefecture where pediatric thyroid cancer cases have been detected other than Fukushima Prefecture. Is this simply coincidental?
On March 20, there were
reports, from Tochigi, Chiba and Gunma Prefectures, of vegetables exceeding the provisional regulation values. Again, here, MHLW merely “requested voluntary suspension of shipment” from each of these prefectures, without actually taking any direct measures. It wasn’t until March 21 that MHWL finally issued an
order for restricting shipments. Furthermore, it’s not as if the suspension of shipments and the radiation testing were being applied to every single food item. Unfortunately, university research labs or research institutes declined to publicize their own measurement data for this article. Apparently, releasing such proof that contaminated food was in distribution after the accident is difficult in the current atmosphere as it goes against the announcement by the government.
There is another circumstance of individuals not having information regarding what kind of food and drinking water they consumed. During my information gathering activities in
Iitate Village, Fukushima Prefecture, in May 2011, someone who evacuated from Iitate Village told me the following story: “Immediately after the accident, about 2,000 Minamisoma residents evacuated to Iitate Village, running away from tsunami. But when they learned Iitate Village became contaminated with radioactive materials, they evacuated from Iitate Village. This means evacuation centers in Iitate Village existed only for 3 to 4 days. But several days later, on March 20, it was discovered that the private water-supply system in Iitate Village was extremely contaminated. It was the evacuees at the evacuation centers that were using the contaminated private water-supply system.”
An
MHLW document released on March 21, 2011, states that, as of 12:30 pm March 20, the private water-supply system in Iitate Village had 956 Bq/L of iodine 131 and 153 Bq/L of iodine 132. The document stated that, as of 8:30 am March 21, there was 492 Bq/L of iodine 131 and 54.1 Bq/L of iodine 132.
According to this document, there is a significant amount of iodine 132 detected, with a half-life of 2-3 hours. By the following day, iodine 131, with a half-life of 8 days, is nearly halved. Why was something with a half-life of 8 days reduced to half the amount by in
one day? Professor Tokonami says, “When it comes to tributaries, a private water-supply system receives intake from various streams, and dilution might be fast.” The half-life of iodine 131 is 8 days, and that of iodine 132 is 2-3 hours. Considering the fact iodine 131 was nearly halved from March 20 to March 21, calculating backwards to March 15 the iodine 131 concentration is estimated to be several tens of thousand Bq/L.
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A radiation monitoring device in Iitate Village shows an ambient radiation level of
0.61 μSv/hour on October 18, 2012, 19 months after the accident.
The radiation level at 6:20 pm on March 15, 2011 was 44.7 μSv/hour.
(Photo credit: Oshidori Ken) |
The man I interviewed in Iitate Village turns out to be a public worker who managed the evacuation centers at the time, and he was extremely regretful that he “inadvertently provided the evacuees with contaminated drinking water.” I interviewed five Minamisoma residents who evacuated to Iitate Village, and none of them was aware of the contamination in the private water-supply system they used during evacuation.
Un-investigated Iodine 131
Is it not necessary to conduct a detailed internal radiation exposure questionnaire survey while people’s memory is still fresh and while information can be traced? How can we complete dose assessment without even conducting surveys that can still be conducted?
Nuclear Safety Commission recommended an additional survey on March 30, 2011, citing inadequacy of thyroid monitoring on 1,080 children. However, the Special Headquarters for Measures to Assist the Lives of Disaster Victims turned down the recommendation stating, “An additional survey is not to be conducted as it may create a significant degree of anxiety for the survey subjects and their families, as well as the local communities.”
After the nuclear accident, residents of Iitate Village had an earnest and urgent request that went unheard: “We would like to have measurements taken of the residents before iodine 131 becomes undetectable.” Then five months later, when no iodine would be detectable at all, it was announced that a whole body counter study will begin to measure the internal exposure dose of Fukushima residents. Now, however, dose assessment is said to be impossible due to “the lack of direct measurements in residents immediately after the accident.” Government experts should have been well aware of the half-life of iodine 131. Why did they not conduct a thorough survey at the time while iodine 131 was still detectable?
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Magenedo Iitate logo sign for the press conference.
(Photo credit: Yutaka Kamimura) |
In April 2011, an organization of young adults from Iitate Village called Magenedo Iitate (literally means
Iitate won’t be beaten) pleaded to various organizations such as Tokyo Electric Power Company (TEPCO), Fukushima Prefectural Office, and MHWL to conduct measurements of the internal exposure dose of children: “We were told that priorities were given to Self-Defense Force soldiers, police officers and firefighters in regards to internal exposure measurements in parts of East Japan around Fukushima, with residents set aside for later time. We asked them to at least measure the internal exposure dose of the children, telling them we would pay our own way to get wherever the internal exposure testing is conducted, even Kyushu or Hokkaido.” At the end, their plea was never answered. Now, they can barely contain their outrage: “They can’t conduct the dose assessment due to lack of direct measurements of the residents in the immediate post-accident period? We begged to have direct measurements taken, for fear of lack of data impeding dose assessment. They waited until the iodine was gone before starting the whole body counter measurements.”
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Magenedo Iitate members at the August 28, 2011 press conference.
(Photo credit: Yutaka Kamimura) |
Internal exposure survey needed
It is not acceptable to disregard what can still be done, such as gathering scattered data (measurements of food, atmosphere, and soil) and redoing a detailed behavior questionnaire, in order to investigate which plume might have been encountered by residents or the contamination level of food that was being consumed by them. Internal exposure survey is included in the Basic Survey of Fukushima Health Management Survey, but it covers only 20 days’ worth of information up to March 31, 2011. Shouldn’t we at least conduct a more detailed investigation on the internal exposure of children diagnosed as “confirmed or suspicious of malignancy,” gathering such information as what they ate during 2011?
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Committee Chair Hokuto Hoshi speaks with a microphone in hand at the May 18, 2015 Oversight Committee meeting.
(Photo credit: Oshidori Ken) |
During the Oversight Committee meeting, Dr. Tsugane voiced his opinion, “How certain is the dose assessment? That should really be evaluated.” However, the Oversight Committee Chairman, Dr. Hokuto Hoshi, always gives the same answer: “It might be true that it is getting late [to conduct dose assessment], and I understand it might only provide a very small clue. Yet I believe that we should do it, so it’s not as if I am ignoring it.” He made exactly the same statement during the 19th Oversight Committee meeting where the Interim Summary for Thyroid Examination was submitted.
This is the 5
th post-accident year. If a study were to be conducted to investigate the internal exposure during 2011 of the children diagnosed as “confirmed or suspicious of malignancy,” we should not wait too long as the longer the wait the more the memory fades. Ordinarily one would conduct an internal exposure survey as soon as possible. But the Oversight Committee Chairman Hoshi keeps putting it off, repeating, “This is a future task for us to discuss and decide.” It has been four years since the Oversight Committee was launched. Chairman Hoshi has not given any concrete statements regarding specific time tables. All he does is keep repeating the same word, “This is a future task.”
An epidemiologist reports the excess occurrence of pediatric thyroid cancer; and clinicians say the excess occurrence is not due to overdiagnosis. Dr. Tsugane says, “Potential for radiation exposure effects might need to be explored even in Initial Screening.” Dr. Shimizu says, “Report of an increase in pediatric thyroid cancer four years after the Chernobyl accident needs verified by evaluating examinations in the first three post-accident years. It cannot be ruled out that there was already an increase before the fourth year.” For the first time, there are differences in opinions within the authority which have explained there were no radiation effects.
What about the detailed dose assessment, then? It is still “under consideration” as if the time has frozen. I agree with the words of Dr. Shimizu: “We must accept new data candidly and figure out how to deal with it.” I sincerely hope the best option is chosen for the sake of the children.
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Oshidori Mako & Ken:
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Oshidori Mako & Ken: DAYS JAPAN editorial members. A married Manzai comedy pair signed to the Yoshimoto Creative Agency.
(Photo credit: Yutaka Kamimura) |
Since the Fukushima nuclear power plant accident, Oshidori Mako & Ken have attended and covered Tokyo Electric’s regularly scheduled press conferences and almost all the committee meetings sponsored by the government or Fukushima Prefecture. They are active in conducting interviews of experts as well as on-site fact-gathering investigations. The number of the Tokyo Electric press conferences attended by Oshidori Mako and Ken is the highest of all the Japanese journalists.
