A Cohort Study of Thyroid Cancer and Other Thyroid Diseases after the Chornobyl Accident: Objectives, Design and Methods

Abstract

The thyroid gland in children is one of the organs that is most sensitive to external exposure to X and gamma rays. However, data on the risk of thyroid cancer in children after exposure to radioactive iodines are sparse. The Chornobyl accident in Ukraine in 1986 led to the exposure of large populations to radioactive iodines, particularly (131)I. This paper describes an ongoing cohort study being conducted in Belarus and Ukraine that includes 25,161 subjects under the age of 18 years in 1986 who are being screened for thyroid diseases every 2 years. Individual thyroid doses are being estimated for all study subjects based on measurement of the radioactivity of the thyroid gland made in 1986 together with a radioecological model and interview data. Approximately 100 histologically confirmed thyroid cancers were detected as a consequence of the first round of screening. The data will enable fitting appropriate dose-response models, which are important in both radiation epidemiology and public health for prediction of risks from exposure to radioactive iodines from medical sources and any future nuclear accidents. Plans are to continue to follow-up the cohort for at least three screening cycles, which will lead to more precise estimates of risk.

Factors associated with serum thyroglobulin in a Ukrainian cohort exposed to iodine-131 from the accident at the Chernobyl Nuclear Plant

“…The details of the screening examination procedure have been previously described (Stezhko et al, 2004;Tronko et al, 2012). Screening consisted of ultrasonography with 7.5-MHz ultrasound probes and thyroid palpation by a trained ultrasonographer, and independent clinical examination and palpation by an endocrinologist.…”

Urinary Iodine and Goiter Prevalence in Belarus: Experience of the Belarus–American Cohort Study of Thyroid Cancer and Other Thyroid Diseases Following the Chornobyl Nuclear Accident

“…Details of the methods of both the Belarus study and the parallel study in Ukraine are available in Stezhko et al (13). In brief, the cohort in Belarus was assembled using a database of thyroid radioactivity measurements taken within 2 months after the Chornobyl accident.…”

A cohort study of thyroid cancer and other thyroid diseases after the Chornobyl accident

“…Members of the cohort under study had direct measurements of thyroid radioactivity in May to June 1986, allowing calculation of their individual thyroid doses of 131 I. [18][19][20] From 1998 through 2000, 13,243 participants underwent the first cycle of screening, which included examination by an endocrinologist, an ultrasound examination, determination of thyroid-stimulating hormone level, urinary iodine, and, if indicated, fine-needle aspiration (FNA) biopsy. 18,19 Ultrasound examinations using a 7.5-megahertz probe routinely targeted the thyroid gland and perithyroid regions, including the jugular (lateral) lymph nodes.…”

“…[18][19][20] From 1998 through 2000, 13,243 participants underwent the first cycle of screening, which included examination by an endocrinologist, an ultrasound examination, determination of thyroid-stimulating hormone level, urinary iodine, and, if indicated, fine-needle aspiration (FNA) biopsy. 18,19 Ultrasound examinations using a 7.5-megahertz probe routinely targeted the thyroid gland and perithyroid regions, including the jugular (lateral) lymph nodes. FNA biopsy was undergone by all patients who had focal thyroid lesions that measured 10 mm in greatest dimension detected either on palpation or on ultrasound and by all patients who had sonographically suspicious lesions (based on hypoechogenicity, irregular shape/contour, microcalcifications, extension through thyroid capsule, interval growth, abnormal adenopathy) that measured from 5 mm to 10 mm in greatest dimension.…”

“…[18][19][20] Cohort members are examined at least every 2 years, and individuals who have nodules identified that are suspicious for cancer are sent to surgery. In this report, we provide a detailed characterization of the pathology of the thyroid cancers detected as a result of the first cycle of screening (from 1998 to 2000) and an analysis of their pathology related to tumor latency.…”