Locoregional late effects of paravascular Thorotrast deposits: Results of the German Thorotrast study

Purpose:The aim of this study was to assess late effects of long-term expos ure to alpha irradiation caused by paravascular Thorotrast deposits. Subjects and methods: 899 patients, who had received the radioactive contra st medium Thorotrast for angiography in the 1930s and 1940s, and 662 contro ls were followed-up since 1968 every two years by standardized clinical and laboratory examinations. Initially, X-ray plain films of the thorax, upper abdomen and the former injection site were performed. In selected patients the sites of paravascular Thorotrast deposits were evaluated by ultrasonog raphy, CT and MRI. Results: Paravascular Thorotrast deposits were detected in 245 patients. Cl inical symptoms related to deposits appeared 10 to 30 years after Thorotras t administration. The severity of symptoms depended on the location and ext ension of granulomas and were mainly caused by fibrosis, nerve paralysis an d vascular changes. Four malignant tumors adjacent to granulomas were obser ved tone soft tissue sarcoma in the groin, two squamous cell carcinomas of the parotid gland and one lymphoepithelial carcinoma of the nasopharynx). M RI including MRA allowed an accurate determination of tissue damage, wherea s the utility of US and CT was restricted due to strong sound attenuation a nd streak artefacts caused by the high X-ray absorption of Thorotrast. Discussion and conclusion: Locoregional late effects of paravascular Thorot rast deposits mainly comprise radiation induced, fibrotic tissue destructio n. The incidence of malignant tumors, in particular sarcomas, adjacent to d eposits, however, is much lower than initially expected.