Results of the German Thorotrast Study

Thorotrast consisted of 25% collidal solution of thorium dioxide. The predominant form of application was intra-arterial injection. About 97% of the injected contrast medium is retained by the organs of the reticulo-endothelial system: liver 59%; spleen 29%; bone marrow 9%. An injection of 25 ml Thorotrast in a 70 kg person causes the following absorbed dose rates: liver 250 mGy/yr; spleen 700 mGy/yr; bone marrow 90 mGy/yr. The German Thorotrast study was started in 1968. It comprises 2.326 Thorotrast patients and 1.890 contemporary matched patients in the control group. At the beginning of the study 899 Thorotrast patients and 662 patients of the control group were alive and have been examined every 2 years. The evaluation of the causes of death demonstrates a statistically significant excess rate of malignant liver tumors, of myeloid leukaemias, of liver cirrhosis and of bone marrow failures. The analysis of the age at death shows a significant loss of life time as a function of dose rate. The results of animal experiments demonstrate that the tumor incidence is dependent on the radiation and not on the colloid itself. (orig.)