Mortality after long-term exposure to radioactive thorotrast: A forty-yearfollow-up survey in Sweden

To evaluate temporal patterns of cause-specific mortality after long-term e xposure to the alpha-particle-emitting contrast medium Thorotrast, we inves tigated a cohort consisting of 693 Swedish patients with neurological disor ders who received Thorotrast during cerebral angiography, with follow-up en ding in 1993, Standardized mortality ratios (SMRs) were calculated as the r atio of observed cases in the cohort to expected cases in the general popul ation, Persons exposed to Thorotrast had significant excesses of all causes of death (SMR = 2.8; 95% CI 2.5-3.0), with similar increases noted for men and women. The largest risks were observed for deaths from hematological c auses (SMR = 16.4; n = 8), cerebrovascular diseases (SMR = 10.1; n = 18), g astrointestinal disorders including liver cirrhosis (SMR = 5.2; n = 36), an d tumors (SMR = 4.7; n = 187), There was a significant decrease in SMR with time since injection for cerebrovascular and circulatory diseases, indicat ive of the impact of underlying neurological disorders. In contrast, the SM R increased significantly with time for tumors and gastrointestinal disease s, suggestive of a detrimental effect of cumulative radiation dose. A signi ficant dose-response relationship was found for all causes of death and mal ignant tumors among all age groups, and since SMR increased with time for t he latter category, this is consistent with an effect of cumulative radiati on exposure on cancer development. However, the findings should be treated with caution, since selection bias may have influenced some of the results. (C) 1999 by Radiation Research Society.