BACKGROUND The increase in the number of childhood thyroid carcinoma cases in Ukraine after the Chernobyl nuclear accident in 1986 prompted the development of a registry of thyroid carcinoma cases at the Institute of Endocrinology and Metabolism in Kiev. In the current study, the authors report the statistical data and clinicomorphologic features of the cases included in this registry. METHODS To study the incidence, and age and gender distribution of thyroid carcinoma in Ukraine, the authors compiled complete clinical information from cases diagnosed and treated at the Institute of Endocrinology and Metabolism and statistical reports submitted to the registry from 27 regions of Ukraine. Morphologic features of the resected tumors were examined and were included in the database. RESULTS During the 5 years preceding the Chernobyl nuclear accident, a total of 59 cases of thyroid carcinoma were identified in the birth to 18 years age group (25 in children age ≤ 14 years and 34 in adolescents ages 15–18 years). Between 1986 and 1997, the total number of thyroid carcinomas in Ukrainian children and adolescents was 577 (358 children and 219 adolescents). Morphologically, the thyroid tumors overwhelmingly were papillary carcinomas, and the majority of these also showed a follicular and/or solid growth pattern. Lymph node metastases and other extrathyroidal spread were common, thus necessitating total thyroidectomy and lymph node dissections in many patients. CONCLUSIONS Between 1990 and 1997, a significant increase in the incidence of thyroid carcinoma was noted in children and adolescents in Ukraine; the group most affected was comprised of the individuals who were age ≤ 5 years in 1986 (the year of the Chernobyl nuclear accident). The largest number of cases occurred in patients living in areas of thyroid radiation doses of ≥0.50 grays. The morphologic features of those thyroid tumors suggest that they are aggressive tumors with a high frequency of lymph node metastases, venous invasion, and extrathyroidal spread. Cancer 1999;86:149–56. © 1999 American Cancer Society.

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After the Chernobyl accident in 1986, about 150,000 monitoring measurements were performed in Ukraine. From this data base, 40,000 measurements were selected for which the results of the reference-source measurements could be analyzed by statistical means. The majority of these measurements are of high quality. In this paper, the uncertainties introduced due to the variabilities of anatomic parameters and the measurement geometry are quantified by measurements using a thyroid-neck phantom. Parameters considered are the thyroid mass, the thickness of the tissue overlying the thyroid as well as the detector-neck distance, the orientation, and the horizontal and vertical position of the detector. The uncertainty introduced due to the variability of these factors corresponds to a coefficient of variation in the range of 25-40% for the measured activity.

Based on the results of 131I thyroid activity measurements in three districts of the Chernigov region (Ukraine), individual doses were calculated and an approach of the age dependence of the average thyroid exposure was derived. Using the relationships between the thyroid doses and the 137Cs deposition as well as the location relative to the Chernobyl Nuclear Power Plant (NPP), age-dependent average thyroid doses were extrapolated also for those settlements of this region where no monitoring measurements have been carried out. The highest doses were found in the west of the region with the lowest distance to the Chernobyl NPP. In this part, the highest mean of the thyroid dose in a settlement was 3.3 Gy for infants and 0.5 Gy for adults. The collective thyroid dose was 31,000 and 27,000 person-Gy for children and adults, respectively. Based on this assessment, 140 and 21 excess thyroid cancer cases are predicted for children and adults, respectively. In the years 1989 to 1991, in the whole contaminated territory of the Ukraine 0.4-1.2 cases per 100,000 children were observed. Although the absolute numbers are very small, this indicates the possibility of an increase in thyroid cancer morbidity among children. The same trend also seems to be indicated in the Chernigov region. A careful epidemiological study in the future is necessary to enable a final evaluation of radioinduced cancers in this region.