Influence Of Ethnic Origin On Estimates Of Thyroid Cancer Risk. F. O. Hoffman and A. I. Apostoaei, A.I., SENES Oak Ridge Inc., Center for Risk Analysis, Oak Ridge, TN
To estimate the risk of thyroid cancer per unit dose of I-131, the background incidence rate for an unexposed population is multiplied by specific risk coefficients (using a relative risk model). The risk coefficients are obtained from epidemiologic studies and contain information about the radiosensitivity of the thyroid gland. Usually, the results of these epidemiological studies are available for cohorts of a mixed as opposed to a given ethnic origin (race). Background incidence rates are obtained from cancer registries and are organized by age, gender and race. Individuals of Asian descent have higher incidence rates of thyroid cancer than whites; African-Americans (blacks) have the lowest incidence rates. Thyroid cancer incidence rates also show increases over time since 1973. These rates of increase are drastically different for whites and blacks. Although some portion of the observed discrepancies in background incidence rates between blacks and whites may be due to socio-economical differences in access to medical care, the marked differences in the rate of increase over time indicate for true differences in radiosensitivity. For Tennessee, we have shown that the risk estimates may vary by 10% to 20% according to the ethnic composition of the population in the area.
Work funded by the State of Tennessee through McLaren/Hart Environmental Services, Inc.
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