Rethinking the Growth Pattern of Thyroid Cancer in Young Patients Based on the Fukushima Database

In response to public concern over radiation exposure after the Fukushima Daiichi nuclear power plant accident of March 11, 2011, the Health Survey of Fukushima Prefecture offered thyroid ultrasonography screening to the 360 000 residents 18 years or younger living in the prefecture at the time of the accident. Approximately 300 000 patients underwent preliminary screening in the 2011 to 2013 period during which radiation effects on thyroid nodules development were expected to be nonexistent. Approximately 2000 individuals in the initial screening met criteria for subsequent screening and approximately 550 of those met criteria for fine-needle biopsy. With biopsy results, approximately 110 patients were identified with cancer or suspected cancer and most of these patients underwent surgery. Consistent with published series of pediatric thyroid cancer, the majority of pathologic diagnoses were papillary carcinoma. The prevalence of carcinoma in this largest-to-date pediatric screening series was 37 cases per 100 000 patients—a number far larger than expected from previous published estimates of pediatric thyroid carcinoma. The overall radiation exposure from the Fukushima accident was much less than that from the Chernobyl accident in 1986 and the high incidence of carcinoma detected was believed to be a result of the unprecedented scope of the ultrasonography screening program rather than from any radiation effects. These findings potentially create cancer risk anxiety in the affected region and possibly imply that a significant proportion of pediatric well-differentiated thyroid carcinomas become dormant or quiescent and never present with clinical disease.

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