Thyroid abnormality trend over time in northeastern regions of Kazakstan, adjacent to the Semipalatinsk Nuclear Test Site: A case review of pathological findings for 7271 patients

From 1949 through 1989 nuclear weapons testing carried out by the former So viet Union at the Semipalatinsk Nuclear Test Site (SNTS) resulted in local fallout affecting the residents of Semipalatinsk, Ust-Kamenogorsk and Pavlo dar regions of Kazakstan. To investigate the possible relationship between radiation exposure and thyroid gland abnormalities, we conducted a case rev iew of pathological findings of 7271 urban and rural patients who underwent surgery from 1966-96. Of the 7271 patients, 761 (10.5%) were men, and 6510 (89.5%) were women. The age of the patients varied from 15 to 90 years. Ov erall, a diagnosis of adenomatous goiter (most frequently multinodular) was found in 1683 patients (63.4%) of Semipalatinsk region, in 2032 patients ( 68.6%) of Ust-Kamenogorsk region and in 1142 patients (69.0%) of Pavlodar r egion. In the period 1982-96, as compared before, there was a noticeable in crease in the number of cases of Hashimoto's thyroiditis and thyroid cancer . Among histological forms of thyroid cancer, papillary (48.1%) and follicu lar (33.1%) predominated in the Semipalatinsk region. In later periods (198 7-96), an increased frequency of abnormal cases occurred among patients les s than 40 years of age, with the highest proportion among patients below 20 in Semipalatinsk and Ust-Kamenogorsk regions of Kazakstan. Given the posit ive findings of a significant cancer-period interaction, and a significant trend for the proportion of cancer to increase over time, we recommend more detailed and etiologic studies of thyroid disease among populations expose d to radiation fallout from the SNTS in comparison to non-exposed populatio n.