MON-508 Clinicopathological Features of Papillary Thyroid Cancer After Fukushima and Chernobyl Accidents

The phenomenon of a sharp increase in the incidence of thyroid cancer worldwide is now under debate. Screening activity, diagnostic improvements or real rise in incidence as a result of unknown carcinogens are discussed. Studies in Belarus after Chernobyl showed that the synergistic influence of radiation and nitrates might lead to an increased thyroid cancer (TC) risk in children. For better understanding of the etiology, we compared the published clinical data of pediatric TC patients after the nuclear emergency of Fukushima with the observations we made after the Chernobyl accident. In a large-scale survey after the Fukushima accident, 300,476 subjects were screened and by September 2018, 191 subjects were diagnosed with thyroid malignancy or suspected malignancy by fine needle aspiration. Mean age of TC patients was 17.8 years at presentation. Mean tumor size was 14.9 mm. Postoperative lymph node metastasis, extra-thyroidal invasion, and pulmonary metastasis were detected in 79%, 45%, and 2.1% of all cases, respectively. Only 4.8% TC cases were staged as low risk pT1aN0M0 (Suzuki et al. 2018). For comparison, in Belarus patients mean age was 13.0 years at presentation (1078 cases), mean tumor size 14.4 mm. Lymph node metastases were observed in 74%, pulmonary metastasis in 11% and extra-thyroidal extension in 48.5 - 64.1% (with respect to latency period). The low risk (pT1aN0M0) TC patients were diagnosed in 19.2% cases. The most of TC cases from Japan and Belarus were clinically significant, not “overdiagnosed” and screened on time. Given that the accidental thyroid doses were very low in Japanese cases, it would be very important to evaluate and compare the exposure to endocrine disruptors as e.g. nitrates and low radiation doses from diagnostic procedures (dental X-ray examination and computed tomography). Referece: Suzuki S, Matsumoto Y, Ookouchi C, Nakano K, Iwadate M, Suzuki S, Nakamura I, Fukushima T, Mizunuma H, Yamashita S, Takenoshita S. The clinicopathological features of childhood and adolescent thyroid cancer in Fukushima after the Fukushima Daiichi nuclear power plant accident. Thyroid. 2018; Supplement 1, (Poster 136).