A Cohort Study of Thyroid Cancer and Other Thyroid Diseases After the Chornobyl Accident: Thyroid Cancer in Ukraine Detected During First Screening

Background: The Chornobyl accident in 1986 exposed thousands of people to radioactive iodine isotopes, particularly 131I; this exposure was followed by a large increase in thyroid cancer among those exposed as children and adolescents, particularly in Belarus, the Russian Federation, and Ukraine. Here we report the results of the first cohort study of thyroid cancer among those exposed as children and adolescents following the Chornobyl accident. Methods: A cohort of 32 385 individuals younger than 18 years of age and resident in the most heavily contaminated areas in Ukraine at the time of the accident was invited to be screened for any thyroid pathology by ultrasound and palpation between 1998 and 2000; 13 127 individuals (44%) were actually screened. Individual estimates of radiation dose to the thyroid were available for all screenees based on radioactivity measurements made shortly after the accident and on interview data. The excess relative risk per gray (Gy) was estimated using individual doses and a linear excess relative risk model. Results: Forty-five pathologically confirmed cases of thyroid cancer were found during the 1998–2000 screening. Thyroid cancer showed a strong, monotonic, and approximately linear relationship with individual thyroid dose estimate (P