Epidemiological, pathological and dosimetric status of Japanese thorotrast patients

In Japan, several thousand people, three-quarters of whom were war-wounded, have been administered Thorotrast. An epidemiological follow-up study on Thorotrast-administered war-wounded veterans was initiated in 1963. The 7th survey of the study was conducted on 286 veterans at the end of 1986, of whom 262 had received Thorotrast intravascularly and 24 by other routes. Of those who had received Thorotrast intravascularly, 58 were alive, 197 had died and 7 could not be traced. The main causes of death were 56 malignant liver tumors, 18 cirrhoses of the liver, 6 blood diseases and 5 cancers of the extrahepatic bile duct. Statistical analysis showed that the incidences of these disorders were significantly higher in the Thorotrast cases than in the controls. The lifespans of Thorotrast administered persons decreased with the amount of Thorotrast injected when compared with those of the controls. Between 1945 and 1990, 357 persons who had been administered Thorotrast intravascularly were autopsied, and 240 malignant liver tumors and 4 malignant peritoneal tumors were found. The incidences of the liver and peritoneal tumors in the Thorotrast autopsies were significantly higher than those in the control autopsies, respectively. Histological examination of the Thorotrast-induced malignant liver tumors revealed a chronological change in the incidences of the histological patterns, especially in those of combined malignant tumors. Dosimetry of Thorotrast autopsy materials revealed the following mean dose rates; 26.1 cGy/year in the liver, 91.2 cGy/year in the spleen and 8.5 cGy/year in the bone marrow.