Mortality among Thorotrast-exposed patients and an unexposed comparison group in the German Thorotrast study

Thorotrast was the brand name of a stabilised colloidal solution of thorium dioxide which was used preferentially as an X-ray contrast medium for arteriography between 1930 and 1950. The administration of the medium led to lifelong chronic α-particle irradiation by thorium decay products, mainly in the organs of deposition. Several epidemiological follow-up studies were set up after recognition of these side-effects among which the German study was the largest. After an extended follow-up, by 2004 only nine out of 2326 originally exposed subjects were still alive (while 151 of the comparison group, which originally numbered 1890 subjects, survived) and partially more than 70 years observation and chronic exposure time could be studied allowing for further observations to be made about long-term mortality effects of Thorotrast exposure. Median life-expectancy was shortened by 14 years and mortality increased, affecting total mortality SMR = 287 for males, SMR = 387 for females) as well as cause-specific, especially liver cancer (SMR = 16,695 and SMR = 12,680, respectively), and the haematopoietic system (SMR = 556 and SMR = 504, respectively), but not lung cancer. Mortality (total and selected cause-specific) increased with cumulative time since first exposure.