CHERNOBYL-RELATED THYROID-CANCER IN CHILDREN OF BYELARUS - A CASE-CONTROL STUDY

The accident at the Chernobyl nuclear power plant on April 26, 1986, r eleased approximately 2 EBq of I-131 and other radioiodine isotopes th at heavily contaminated southern Belarus. An increase in thyroid cance r reported in 1992 and attributed to the Chernobyl accident was challe nged as possibly the result of intensive screening. We began a case-co ntrol study to test the hypothesis that the Chernobyl accident caused the increase in thyroid cancer. Records of childhood thyroid cancer in the national therapy centers in Minsk in 1992 yielded 107 individuals with confirmed pathology diagnoses and available for interview. Pathw ays to diagnosis were (1) routine endocrinological screening in 63, (2 ) presentation with enlarged or nodular thyroid in 25 and (3) an incid ental finding in 19. Two sets of controls were chosen, one matched on pathway to diagnosis, the other representing the area of heavy fallout , both matched on age, sex and rural/urban residence in 1986. The I-13 1 dose to the thyroid was estimated from ground deposition of Cs-137, ground deposition of I-131, a data bank of 1986 thyroid radiation meas urements, questionnaires and interviews. Highly significant difference s were observed between cases and controls (both sets) with respect to dose. The differences persisted within pathway to diagnosis, gender, age and year of diagnosis, and level of iodine in the soil, and were m ost marked in the southern portion of the Gomel region. The case-contr ol comparisons indicate a strong relationship between thyroid cancer a nd estimated radiation dose from the Chernobyl accident. (C) 1998 by R adiation Research Society.