Fukushima: Excess Occurrence of children’s thyroid cancer not due to overdiagnosis

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.

Oshidori Mako Interviews Experts Regarding Excess Occurrence of Pediatric Thyroid Cancer in Fukushima, Fukushima Voice, English Version 6 Aug 15,

This is a translation of an article written by Oshidori Mako and published in the July issue of DAYS JAPAN, posted here with permission of Oshidori Mako. Pediatric Thyroid Cancer in Fukushima

The Thyroid Examination Assessment Subcommittee of
the Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey

Admits Excess Occurrence of Pediatric Thyroid Cancer

112 children have been diagnosed with “confirmed or suspicious pediatric thyroid cancer” during Initial Screening in the pediatric thyroid examination, covering about 370,000 children aged 18 or younger, conducted since the Fukushima nuclear power plant accident.

In Full-Scale Screening or second round screening, 15 children were newly diagnosed similarly.

This was an unexpected result even for physicians.

On May 18, 2015, the Oversight Committee Meeting for the Fukushima Health Management Survey released a summary by the Thyroid Examination Assessment Subcommittee stating that pediatric thyroid cancer in Fukushima children was ”several tens of times larger“ than the pre-accident level.

The central and prefectural governments have desperately continued to deny excess occurrence of pediatric thyroid cancer and causality between pediatric thyroid cancer and the accident.

However, now, the monolith built by the experts is beginning to falter.

Text by Oshidori Mako

How one epidemiologist explains “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 theSubcommittee hereafter) to the 19th Prefectural Oversight Committee Meeting for the Fukushima Health Management Survey (referred to as theOversight 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 Screeningis 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 Subcommitteemembers. Dr. Tsugane is an epidemiologist and director of of Research Center for Cancer Prevention and Screening at the National Cancer Center.

Dr. Tsugane submitted to the 4th session of the Subcommittee (held on November 11, 2014) a document titled “The estimated number of prevalent cases of thyroid cancer in Fukushima Prefecture.” The phrase, “several tens of times larger,” in the Interim Summary is derived from this document………..

(*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 increased 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.”……..

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………

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. …. http://fukushimavoice-eng2.blogspot.jp/2015/08/oshidori-mako-interviews-experts.html