The March 25, 2016 Chicago Tribune editorial, “The children of Fukushima: When medical tests mislead” is misleading on its own regarding the childhood thyroid cancer situation in Fukushima Prefecture, Japan.
Differences in cancer rates by distance from the accident site and contamination levels may not be obvious, but an epidemiological analysis by Tsuda et al. (http://journals.lww.com/epidem/Fulltext/2016/05000/The_Authors_Respond.37.aspx) found a dose response tendency with proximity to the accident site after adjusting for the length of time between the accident and the time of screening. It is also important to remember only 1,080 children had their thyroid exposure doses directly measured and that is only 0.36% of 300,000 children who underwent thyroid ultrasound examination. Taken under high background levels, the doses are far from being accurate.
Children younger than age 5 showed an increased rate of thyroid cancer beginning at 4-5 years after the Chernobyl accident, so the first 3 years after the Fukushima accident, covered by the completed first round screening, would not expect to see that age group affected. The first cancer case was diagnosed about 17 months after the accident, not within a year, and some of these early cases might have been the result of radiation exposure promoting the growth of latent cancer that might not have become large enough to be detected until much later in life if unexposed to radiation.
Comparison with three other prefectures where one cancer case was diagnosed in 4,365 subjects is invalid as its small sample size lacks the necessary statistical power. The Korean screening is in adults and should not be compared with children.
It is true that unnecessary medical testing can lead to overdiagnosis and overtreatment, but the clinical information provided by Fukushima Medical University, such as metastasis and physical proximity of tumor to other vital structures, validates surgical interventions for the majority of the operated cases in Fukushima. Thyroid cancer is believed to grow slowly, but 80% of thyroid cancer cases discovered in the ongoing second round screening had no suspicious findings in the first round screening only 2-3 years earlier.
It is not just a cancer death but cancer diagnosis itself that is concerning for patients and their loved ones, and the causality should not be prematurely prejudged. A lesson of the Fukushima children may be the importance of conducting a timely and adequate collection of the exposure data and a comprehensive evaluation of data in a transparent and unbiased manner.
Yuri Hiranuma, D.O.
Member, Radiation and Health Committee
Physicians for Social Responsibility