Thorotrast-induced liver cancer: results of the German Thorotrast study

Aims: The X-ray contrast medium Thorotrast, used worldwide between 1930 to 1950 predominantly for arteriography, consisted of a colloidal solution of thorium dioxide. The radioactive thorium-232 (half-life 1.4x10(10) years) i s stored lifelong in the organs of the reticulo-endothelial system after in travascular injection, causing chronic exposure to alpha radiation. The aim of the German Thorotrast study is the assessment of radiation late effects and the calculation of risk estimates. Material and methods: The German Thorotrast study started in 1968 as a coho rt study and comprises 2326 Thorotrast patients and 1890 patients of a matc hed control group. The Thorotrast patients who were still alive at the begi nning of the study were examined by X-ray plain films of the upper abdomen and of the injection site of the contrast medium as well as by whole-body c ounter measurements. At the beginning we offered the patients ultrasound an d later on CT and MRI at regular intervals for early detection of liver can cer. Results: To date 454 primary liver cancers have been registered in the grou p of Thorotrast patients compared to 3 cases in the control group. With the help of modern imaging methods relatively small liver cancers were detecte d and could be surgically removed. Discussion: There is a correlation between the mean accumulated dose to the liver and the incidence of liver cancer. The cumulative risk for liver mal ignancies is about 600 diseases per 10(4) persons whose liver was exposed t o 1 Gy. Also the incidence of liver cirrhosis is correlated with the mean a ccumulated dose to the liver.