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May 2015 Interim Summary Regarding Thyroid Examination: Unofficial English Translation


At the 19th Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey held on May 18, 2015, an Interim Summary was submitted by the Thyroid Examination Assessment Subcommittee. Although it is called the "Interim Summary," this is essentially the final report by this particular subcommittee. As is customary with Japanese governmental committees, the end of the fiscal year calls for the submission of a summary report, often followed by the prearranged dissolution of the committee.

Below is a complete, unofficial English translation of the Interim Summary. (It has been checked by one of the officials for accuracy).

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The 19th Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey (May 18, 2015)

Interim Summary Regarding Thyroid Examination

Thyroid Examination Assessment Subcommittee, Prefectural Oversight Committee Meeting for Fukushima Health Management Survey, March 2015

The Thyroid Examination Assessment Subcommittee of the Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey was established at the 12th Prefectural Oversight Committee Meeting for Fukushima Health Management Survey held on August 20, 2013. There it was decided to establish a subcommittee specific to the thyroid examination within the Oversight Committee in order to verify and evaluate methods and results of the examination and to disseminate information to Fukushima residents. The first session of the Subcommittee convened on November 27, 2013.

The Subcommittee has deliberated the validity of the scientific, medical and ethical basis for the examination results and their analysis, the administrative responses, the follow-up survey, and the mental care for the residents, from the standpoint of the examination, which is drawing a high interest from the international community. Below is the summary of discussions by the Subcommittee:


1. Assessment of the examination results, responses, and treatment from Initial Screening

Initial Screening (first-round screening) beginning in October 2011 targeted approximately 300,000 Fukushima residents who were 18 or younger at the time of the accident. So far 112 have been diagnosed with thyroid tumors which are “malignant or suspicious for malignancy” as a result of FNAB (fine-needle aspiration biopsy). 99 have been operated on, leading to confirmed diagnosis of 95 cases of papillary thyroid cancer, 3 cases of poorly differentiated thyroid cancer, and 1 benign nodule (data as of March 31, 2015).

The number of cancer cases in the examination result is several tens of times larger than the number of patients estimated from incidence statistics of thyroid cancer analyzed in the regional cancer registry in Japan. This may be interpreted as the result of either excessive occurrence due to radiation exposure or over-diagnosis (i.e. diagnosis of cancer which is neither life-threatening nor symptomatic). There were opinions that, based on scientific knowledge up to know, the possibility of the former (excess occurrence) could not be denied completely, but it was more likely to be the latter (over-diagnosis).

On the other hand, there was an opinion that even if the increase was due to over-diagnosis, if it weren’t for the early diagnosis and treatment there was a possibility for the majority of cases to become symptomatic or life-threatening cancer in several years or even later. 

In addition, if it were papillary thyroid cancer, its biological features would allow for an option of regular follow-up without treatment. Risk assessment of diagnosis and treatment of papillary thyroid cancer detected during screening, including surgical indications, should be left to specialists.

※ Current diagnosis and treatment are based on the clinical guidelines of the Japan Society of Thyroid Surgery. However, there was an opinion calling for a separate clinical guideline appropriate for the current situation in Fukushima or for the pediatric thyroid cancer because the screening is being conducted in asymptomatic individuals and also the prognosis of papillary thyroid cancer is much better in children than in adults.

※ A concurrent improvement in cancer registry was suggested so that all cases of thyroid cancer are recorded. 


2. Assessment of radiation effects

At present it is not possible to conclude whether thyroid cancer cases detected during screening are radiogenic. According to Initial Screening which was completed, thyroid cancer cases detected so far are considered unlikely to be due to radiation effects because of two reasons: 1) exposure dose is much less than in Chernobyl, and 2) no cancer cases have been detected in those who were aged five or younger at the time of the accident. Nevertheless, a long-term, continuing study is essential in order to assess the effects of radiation exposure.

In addition, information on internal exposure dose from radioactive iodine in the early post-accident period is extremely important in determining the effect of the accident. Thus coordination with such dose assessment studies should always be included in advancing the thyroid examination.

On the assumption thyroid cancer might occur due to radiation exposure in the future, it is necessary at this time to consider in advance how to  quantify the size of effect that can be confirmed and the type of data or analysis that could be used to confirm it.


3. Covering medical expenses with government funds

It is difficult to identify the cause of individual thyroid cancer cases. However, as a group, many patients undergoing confirmatory examination end up receiving the medical care they would not have had to receive, at least for the time being (or perhaps in lifetime), if it weren’t for the screening. Thus, if they end up receiving regular medical care with insurance due to their participating in screening, at this time it is desirable for the government to cover their medical expenses incurred after the confirmatory examination.


4. Follow up of the eligible subjects

It is critical to conduct a follow-up survey of the subjects eligible for thyroid examination, especially those who were infants and toddlers at the time of the accident, in order to assess the occurrence and the prognosis of thyroid cancer. 

Also, it is important to thoroughly consider how to follow the age group that will increasingly move out of Fukushima Prefecture (such as to attend college and work). This is an important point in an epidemiological follow-up study.


5. Disclosure of examination results

The establishment of a re-evaluation system is suggested where the anonymous examination results are re-evaluated with transparency by a team including many researchers.
This re-evaluation should be accompanied by careful consideration of privacy protection. 


6. Future thyroid examinations

The nuclear power plant accident brought to Fukushima residents not only “unnecessary exposure” but also the risk burden of “potentially unneeded diagnosis and treatment of thyroid cancer.” However, in regards to the thyroid examination, it is necessary to consider the following points: the possibility cannot be denied that future thyroid cancer occurrence might be due to radiation exposure from the accident; the wishes of many residents to undergo the examination in order to relieve anxiety; and the need for an epidemiological assessment into the existence of the increased occurrence of thyroid cancer due to the effects of the accident, for the purpose of informing residents as well as domestic and international communities. 

Thus, the current thyroid examination should be continued, with a conditional policy to obtain consent of the residents. It should be continued within the examination structure allowing the assessment of the presence or absence of an increased occurrence of radiation-induced thyroid cancer. Also the residents should receive an easily comprehensible explanation that: there may be detriments as well as benefits to examination; and that (papillary) thyroid cancer is the type of cancer whose initial presentation at the time of detection may not necessarily progress to a life-threatening condition (i.e. it has a good prognosis). 

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