Abstract
The intravascular injection of the formerly used contrast medium Thorotrast —a colloidal suspension of thoriumdioxide— causes a chronic exposure to α-particles especially in the organs of the reticuloendothelial system. The German Thorotrast Study comprises 2326 Thorotrast patients and 1890 contemporary matched patients in the control group to be evaluated. 899 Thorotrast patients and 662 controls had clinical and biophysical follow-up examinations every two years since 1969. The recent most important results of the study are: A high excess rate of primary liver cancer (410/2) was observed beginning after the 15th year of exposure. 31% of the tumors are combined with cirrhosis and 6% with other neoplastic diseases. A clear (mean) dose rate effect relationship exists. The tumor frequency depends on the time of exposure or the cumulative dose to the liver respectively and not primarily on the age at injection. The lowest cumulative doses at 10 years before diagnosis of liver cancer were about 2 Gy. Risk estimates for liver cancer after 40 years of exposure are 500 malignant tumors per 104 person-Gy for men and 300 for women.
A high excess rate exists also for leukaemias (excluding CLL) starting already 5 years after Thorotrast injection (39/4). The lowest cumulative doses to the red bone marrow at time of death were about 0.5 Gy. According to the present result, an excess rate can be expected for carcinomas of the extrahepatic bile ducts, pancreas, oesophagus, larynx, as well as Non-Hodgkin''s lymphomas, bone sarcomas, plasmacytomas and mesotheliomas.
