1998 results of the first series of follow-up studies on Japanese Thorotrast patients and their relationships to an autopsy series

The 1998 survey of the first series of epidemiological studies of Japanese Thorotrast patients revealed that 18 (6.9%) were alive and 244 (93.1%) had died among 262 war-wounded veterans to whom Thorotrast had been administere d intravascularly. Of 1,630 age- and sex-matched controls, 525 (32.2%) were alive and 1,105 (67.8%) had died. These results indicated a shortening of the life span in patients who had received Thorotrast compared to their con trols. Of the patients in the Thorotrast group, the main causes of death we re liver malignancies (79, 30.2%), liver cirrhosis (20, 7.6%), blood diseas es (9, 3.4%), and cancers of the extrahepatic bile duct (5, 1.9%). Statisti cal analyses by the chi(2) test and estimation of the relative risk (risk r atio) showed that the incidences of these disorders were significantly high er in the Thorotrast group than in the controls. In the 54-year period from 1945 to 1998, our autopsy series was enlarged to include 398 individuals: 386 injected with Thorotrast intravascularly and 12 injected by other route s. Results of analyses of the 386 autopsy cases given Thorotrast intravascu larly were as follows: 263 cases (68.1%) of liver malignancies, 28 cases (7 .3%) of liver cirrhosis, 29 cases (7.5%) of blood diseases, 16 cases (4.1%) of lung cancer, 4 cases (1.0%) of malignant peritoneal tumors, 2 cases (0. 5%) of bone sarcomas, and 1 case (0.3%) of hemangiosarcoma of the spleen. T he relative risks of liver malignancies, blood diseases, bone sarcomas, mal ignant peritoneal tumors, and hemangiosarcoma of the spleen manifested sign ificantly higher ratios in the Thorotrast autopsy cases (ratio of proportio n) than in the autopsy control cases. Histological studies of these autopsi ed cases revealed that Thorotrast-induced fiver malignancies showed remarka ble differences in the proportions of histological types of tumors from tho se of non-Thorotrast liver malignancies since 1975. However, in this survey , we noted a remarkable increase in the incidence of liver malignancy of mu ltiple histological types compared to that in histological controls. Based on the results of our 1998 survey, we estimated attributable risks of Thoro trast-induced liver malignancies and blood diseases in the life span. Resul ts showed 523 liver malignancies per 10(4) person Gy and 150 blood diseases per 10(4) person Gy for Japanese male Thorotrast carriers (wasted dose 10 years). (C) 1999 by Radiation Research Society.