The protocol and preliminary baseline survey results of the thyroid ultrasound examination in Fukushima

Abstract

After the Fukushima nuclear power plant accident on March 11, 2011, the public of Japan became particularly concerned about the possibility of an increased risk of childhood thyroid cancer, similar to what was observed after the Chernobyl’s accident. Due to serious public health perception, there was an urgency to evaluate the baseline levels of childhood thyroid status in Fukushima prefecture. Therefore we have commenced a thyroid ultrasound examination (TUE) survey of the approximately 360,000 pediatric inhabitants (0 to 18 years of age) who lived in Fukushima at the time of the accident in October 2011. The subjects were divided into three categories according to the standardized diagnostic criteria of ultrasound findings. Category A contained the subjects whose TUE findings were intact or benign. Category B were recommended a confirmatory TUE. Category C was recommended an immediate confirmatory TUE. Results: The survey of 40,302 subjects in the first year was completed in March, 2013. There were 40,097 (99.5%), 205 (0.50%) and 0 subjects in categories A, B and C, respectively. Of the 82 category B subjects who underwent FNAC, 12 were diagnosed with a malignant tumor or were suspected to have malignancy. The 12 subjects received thyroid surgery and 11 thyroid cancers and one benign nodule were confirmed histologically after surgery. This is the first large-scaled TUE survey to employ sophisticated ultrasound screening and aim to evaluate the baseline frequency of childhood thyroid nodules and cysts. The results will become the golden standard of future comparative TUE in Fukushima, Japan.