Pronounced deficiency in T-cells and lymphocyte chromosomal aberrations in a patient with sarcoidosis, myelofibrosis and acute leukaemia following thorotrast angiography

A patient exposed to thorotrast angiography developed sarcoidosis 21 years after the injection and myelofibrosis 13 years later. On the latter occasion an extreme deficiency in circulating lymphocytes forming rosettes with sheep erythrocytes (T-cells) was observed and a large fraction of the cells had chromosomal aberrations. Acute leukaemia developed 1 year later. The multiple clinical symptoms may be related to radiation-induced destruction of bone marrow tissue, mutations in haemopoietic cells and depression of cell-mediated immunity.

[Electrophoretic and immunochemical research of rat urine proteins in dynamics after intravenous injection of thorium dioxide (thorotrast)]

Rats were treated with a single intravenous injection of thorotrast (thorium dioxide)--the source of alpha-rays. Dynamic investigation of urine protens of rats by methods of electrophoresis and immunoelectrophoresis was carried out during 22 months after thorotrast injection. Already the month after drug injection the selectivity of tubular reabsorbtion was disturbed. Three months after thorotrast injection the content of urinal proteins of tissue (in particular renal) origin was decreased. Finally the selectivity of renal filtration of proteins was damaged 4-6 months after thorotrast introduction. Serum proteins which were absent in normal urine (for example transferrin and lipoproteins) appeared in urine of affected rats. The urine proteins of serum origin were less degraded than those in normal urine. The alterations of glomerular filtration was increased up to 20-22 months when the spectrum of urine proteins became similar to the spectrum of serum proteins. The death of treated rats was occurred in this period. Thus the monitoring of urine proteins of rats treated with alpha-ray producing preparation throtrast allows to register the successive alterations of reabsorbtion, excretion and filtration functions of kidney.

Thorium dioxide-related haemangiosarcoma of the liver

Rare tumours of the liver are occasionally seen; thorium dioxide-related haemangiosarcoma of the liver, with an estimated frequency of 0.14 to 0.25 per million in the normal population, is one of these. Causes, epidemiology and pathobiology are described related to a clinical case of angiosarcoma. A differentiation of hepatic tumours with imaging techniques is presented. Last, a short review on up-to-date treatment of haemangiosarcoma is discussed. Lessons can always be learned from history: will the contrast agent gadolinium be the Th232 of this era?

Cholangiocarcinoma in association with Thorotrast exposure

Thorotrast is a colloidal suspension of thorium dioxide that was used as an intravascular contrast agent until the 1950's. It is retained by the reticuloendothelial system, and because it emits densely ionizing radioactivity thorium dioxide it is carcinogenic. Two patients with prior thorium dioxide exposure diagnosed with cholangiocarcinoma and recently treated at the Massachusetts General Hospital are presented. Radiology, treatment, pathologic findings, and relevant literature are discussed.

Allelotypic Characteristics of Thorotrast-Induced Intrahepatic Cholangiocarcinoma: Comparison to Liver Cancers not Associated with Thorotrast

To elucidate the genetic alterations that are specific to Thorotrast-induced liver cancers and their possible roles in tumorigenesis, we analyzed loss of heterozygosity (LOH) at 37 loci. Our previous study of liver cancers that were not associated with Thorotrast found LOH at 9 of these loci to be characteristic of intrahepatic cholangiocarcinoma (ICC), at 19 to be characteristic of hepatocellular carcinoma (HCC), and at 9 to be common to both ICC and HCC. LOH analysis was also performed in tissues of cholangiolocellular carcinoma, which is thought to originate from a common stem cell progenitor of hepatocytes and bile duct epithelial cells. We found frequent LOH at D4S1538, D16S2624 and D17S1303 to be common to all the subtypes of liver cancers, independent of the specific carcinogenic agent. In contrast, LOH at D4S1652 generally was not observed in Thorotrast-induced ICC. LOH analysis revealed that Thorotrast-induced ICC shares some LOH features with both ICC and HCC that were not induced by Thorotrast; however, it is more similar to ICC than to HCC in terms of genetic changes. This study could narrow down the crucial chromosomal loci whose deletions are relevant to hepatobiliary carcinogenesis irrespective of the carcinogenic agent. The study of LOH at loci other the those crucial ones may help us understand how the phenotype of liver cancers is determined.

Site-specific cancer incidence and mortality after cerebral angiography with radioactive thorotrast

Few opportunities exist to evaluate the carcinogenic effects of long-term internal exposure to alpha-particle-emitting radionuclides. Patients injected with Thorotrast (thorium-232) during radiographic procedures, beginning in the 1930s, provide one such valuable opportunity. We evaluated site-specific cancer incidence and mortality among an international cohort of 3,042 patients injected during cerebral angiography with either Thorotrast (n = 1,650) or a nonradioactive agent (n = 1,392) and who survived 2 or more years. Standardized incidence ratios (SIR) for Thorotrast and comparison patients (Denmark and Sweden) were estimated and relative risks (RR), adjusted for population, age and sex, were generated with multivariate statistical modeling. For U.S. patients, comparable procedures were used to estimate standardized mortality ratios (SMR) and RR, representing the first evaluation of long-term, site-specific cancer mortality in this group. Compared with nonexposed patients, significantly increased risks in Thorotrast patients were observed for all incident cancers combined (RR = 3.4, 95% CI 2.9-4.1, n = 480, Denmark and Sweden) and for cancer mortality (RR = 4.0, 95% CI 2.5-6.7, n = 114, U.S.). Approximately 335 incident cancers were above expectation, with large excesses seen for cancers of the liver, bile ducts and gallbladder (55% or 185 excess cancers) and leukemias other than CLL (8% or 26 excess cancers). The RR of all incident cancers increased with time since angiography (P < 0.001) and was threefold at 40 or more years; significant excesses (SIR = 4.0) persisted for 50 years. Increasing cumulative dose of radiation was associated with an increasing risk of all incident cancers taken together and with cancers of the liver, gallbladder, and peritoneum and other digestive sites; similar findings were observed for U.S. cancer mortality. A marginally significant dose response was observed for the incidence of pancreas cancer (P = 0.05) but not for lung cancer. Our study confirms the relationship between Thorotrast and increased cancer incidence at sites of Thorotrast deposition and suggests a possible association with pancreas cancer. After injection with >20 ml Thorotrast, the cumulative excess risk of cancer incidence remained elevated for up to 50 years and approached 97%. Caution is needed in interpreting the excess risks observed for site-specific cancers, however, because of the potential bias associated with the selection of cohort participants, noncomparability with respect to the internal or external comparison groups, and confounding by indication. Nonetheless, the substantial risks associated with liver cancer and leukemia indicate that unique and prolonged exposure to alpha-particle-emitting Thorotrast increased carcinogenic risks.

Redistribution of thorotrast into a liver allograft several years following transplantation: a case report

Thorotrast was used as a radiographic contrast agent in the United States from about 1930 to the mid-1950 s. Its use was discontinued when it was recognized that its radioactivity caused long-term deleterious effects. Such long-term sequelae of intravascular Thorotrast injection include, most notably, hepatic and hematologic malignancies and hepatic fibrosis. Some patients who had received Thorotrast subsequently received liver transplants. However, it was not known whether or not Thorotrast could become redistributed within the new allograft. A single report in 1994 demonstrated that radioactivity was detected by gamma-ray spectroscopy in liver allografts shortly after transplantation. No report has identified Thorotrast in the allografts of long-term transplant survivors, and the redistribution of Thorotrast into allografts has not been documented histologically or by electron microscopy. We report a case of recurrent Thorotrast into a liver allograft 10 years post-transplant. We evaluated the native liver and allograft specimens for the presence of thorium utilizing light microscopy, electron microscopy and electron X-ray microanalysis. This case report demonstrates for the first time the redistribution of Thorotrast into a long-surviving liver allograft using histologic, electron microscopic and X-ray microanalysis techniques.

A biologically based model for liver cancer risk in the Swedish thorotrast patients

Data on liver tumors among 416 Swedish patients who were exposed to Thorotrast between 1930 and 1950 were analyzed with the biologically based two-step clonal expansion (TSCE) model. For background data, the Swedish Cancer Register for the follow-up period 1958 to 1997 was used. Effects of radiation on the initiating mutation and on the clonal expansion rate explained the observed patterns well. The TSCE model permits the deduction of several kinetic parameters of the postulated tumorigenesis process. Dose rates of 5 mGy/year double the spontaneous initiation rate. The clonal expansion rate is doubled by 80 mGy/year, and for females it reaches a plateau at dose rates beyond 240 mGy/year. For males the plateau is not significant. The magnitude of the estimated promoting effect of radiation can be explained with a moderate increase in the cell replacement probability for the intermediate cells in the liver, which is strikingly similar to the situation in lung tumorigenesis.

Mortality after radiological investigation with radioactive Thorotrast: a follow-up study of up to fifty years in Portugal

Cerebral angiography using a radioactive radiological contrast medium, Thorotrast, was pioneered by Moniz in Portugal in the 1920s. Thorotrast is retained by the reticuloendothelial system, with a biological half-life of several hundred years, so that such patients suffer lifetime exposure to internal radiation. We studied mortality in Portuguese patients who were administered Thorotrast during the period 1928-1959 and in a comparison group of patients who received nonradioactive contrast agents. There were 1096 systemically exposed, 1014 unexposed, and, unique to the Portuguese study, 240 locally exposed Thorotrast patients who were successfully traced and followed up to the end of 1996. Mortality was significantly raised among systemically exposed Thorotrast patients relative to those unexposed for all causes [relative risk (RR) = 2.63], all neoplasms (RR = 6.72), liver cancer (RR = 42.4), chronic liver disease (RR = 5.12), other non-neoplastic diseases of the digestive system (RR = 4.87), neoplastic (RR = 21.9) and non-neoplastic hematological disorders (RR = 6.00), and non-neoplastic diseases of the respiratory system (RR = 4.31). Risks for most of these conditions increased significantly with time since first administration of the contrast medium and with cumulative alpha-particle radiation dose. Mortality was also significantly raised for non-neoplastic disorders of the nervous system (RR = 12.7) and ill-defined conditions (RR = 3.74), but these associations are likely to reflect the initial diagnosis, not Thorotrast exposure, because risks declined significantly with time and/or dose. There were no significant excess deaths from oropharyngeal or nasal cancers, or from any other cause, among patients exposed to Thorotrast locally for visualization of the perinasal sinuses, and no clear trend in risk with time since exposure. This study shows an association between systemic, but not local, exposure to Thorotrast and mortality from liver cancer, chronic liver disease, and neoplastic and non-neoplastic hematological disorders, with risks for these conditions remaining high for over 40 years after administration. Liver conditions, but not hematological disorders, showed a strong and consistent gradient with cumulative alpha-particle radiation dose.

Quantitative comparisons of cancer induction in humans by internally deposited radionuclides and external radiation

PURPOSE

To compare quantitative estimates of lifetime cancer risk in humans for exposures to internally deposited radionuclides and external radiation. To assess the possibility that risks from radionuclide exposures may be underestimated.

MATERIALS AND METHODS

Risk estimates following internal exposures can be made for a small number of alpha-particle-emitting nuclides. (1) Lung cancer in underground miners exposed by inhalation to radon-222 gas and its short-lived progeny. Studies of residential (222)Rn exposure are generally consistent with predictions from the miner studies. (2) Liver cancer and leukaemia in patients given intravascular injections of Thorotrast, a thorium-232 oxide preparation that concentrates in liver, spleen and bone marrow. (3) Bone cancer in patients given injections of radium-224, and in workers exposed occupationally to (226)Ra and (228)Ra, mainly by ingestion. (4) Lung cancer in Mayak workers exposed to plutonium-239, mainly by inhalation. Liver and bone cancers were also seen, but the dosimetry is not yet sufficiently good enough to provide quantitative estimates of risks. Comparisons can be made between risk estimates for radiation-induced cancer derived for radionuclide exposure and those derived for the A-bomb survivors, exposed mainly to low-LET (linear energy transfer) external radiation. Data from animal studies, using dogs and rodents, allow comparisons of cancer induction by a range of alpha- and beta-/gamma-emitting radionuclides. They provide information on relative biological effectiveness (RBE), dose-response relationships, dose-rate effects and the location of target cells for different malignancies.

RESULTS

For lung and liver cancer, the estimated values of risk per Sv for internal exposure, assuming an RBE for alpha-particles of 20, are reasonably consistent with estimates for external exposure to low-LET radiation. This also applies to bone cancer when risk is calculated on the basis of average bone dose, but consideration of dose to target cells on bone surfaces suggests a low RBE for alpha-particles. Similarly, for leukaemia, the comparison of risks from alpha-irradiation ((232)Th and progeny) and external radiation suggest a low alpha RBE; this conclusion is supported by animal data. Risk estimates for internal exposure are dependent on the assumptions made in calculating dose. Account is taken of the distribution of radionuclides within tissues and the distribution of target cells for cancer induction. For the lungs and liver, the available human and animal data provide support for current assumptions. However, for bone cancer and leukaemia, it may be that changes are required. Bone cancer risk may be best assessed by calculating dose to a 50 micro m layer of marrow adjacent to endosteal (inner) bone surfaces rather than to a single 10 micro m cell layer as currently assumed. Target cells for leukaemia may be concentrated towards the centre of marrow cavities so that the risk of leukaemia from bone-seeking radionuclides, particularly alpha emitters, may be overestimated by the current assumption of uniform distribution of target cells throughout red bone marrow.

CONCLUSIONS

The lifetime risk estimates considered here for exposure to internally deposited radionuclides and to external radiation are subject to uncertainties, arising from the dosimetric assumptions made, from the quality of cancer incidence and mortality data and from aspects of risk modelling; including variations in baseline rates between populations for some cancer types. Bearing in mind such uncertainties, comparisons of risk estimates for internal emitters and external radiation show good agreement for lung and liver cancers. For leukaemia, the available data suggest that the assumption of an alpha-particle RBE of 20 can result in overestimates of risk. For bone cancer, it also appears that current assumptions will overestimate risks from alpha-particle-emitting nuclides, particularly at low doses.

Thorotrast-induced cholangiocarcinoma: case report

Thorotrast, a contrast medium used extensively before being banned in 1950s, delivers a densely ionizing, high linear energy transfer type of radiation that predisposes to malignancies. We report a case of peripheral cholangiocarcinoma and describe its computed tomographic and magnetic resonance imaging features in a patient who developed it 48 years after exposure to Thorotrast.

The relationship between internally deposited alpha-particle radiation and subsite-specific liver cancer and liver cirrhosis: an analysis of published data

Chronic exposure to high LET radiation has been shown to cause liver cancer in humans based on studies of patients who received Thorotrast, a colloidal suspension of thorium dioxide formerly used as a radiological contrast agent, and on studies of Russian nuclear weapons workers exposed to internally ingested plutonium. Risk estimates for these exposures and specific subtypes of liver cancer have not been previously reported. Combining published data with tumor registry data pertinent to the Thorotrast cohorts in Germany, Denmark, Portugal, and Japan and to Russian workers, we generally found significantly elevated risks of three major histologic types of liver tumors: hepatocellular carcinoma (HCC), cholangiocarcinoma (CC), and hemangiosarcoma (HS) for Thorotrast exposures. In contrast, HS was the only liver tumor significantly associated with the lower alpha-particle doses experienced by the Russian workers. Excess cases per 1,000 persons exposed to Thorotrast were similar for the three liver cancer subtypes but lower for plutonium exposure. Odds ratios (OR) of HS and CC for Thorotrast were from 26 to 789 and from 1 to 31 times higher than those for HCC, respectively. ORs of liver cirrhosis for Thorotrast exposure ranged from 2.7 (95% confidence interval (CI): 2.2-3.4) to 6.7 (5.1-8.7).

Microsatellite instability in thorotrast-induced human intrahepatic cholangiocarcinoma

Thorotrast, a colloidal suspension of radioactive (232)ThO(2) that emits alpha particles, was used as a radiographic contrast during World War II. It is known to induce liver cancers, most frequently ICC, decades after injection. Since radiation induces genomic instability, we analyzed MSI in Thorotrast-induced ICC. The frequency of MSI(+) cases was 62.5% in Thorotrast ICC, whereas it was 22.7% in non-Thorotrast ICC. However, frameshift mutations of mononucleotide repeats were not observed in Thorotrast ICC. In addition, the MSI(+) phenotype was not associated with the quantity of Thorotrast deposited or the latency period of ICC induction. Promoter regions of both the hMLH1 and the hMSH2 MMR genes tended to be hypermethylated in the tumor part compared to the adjacent nontumor part in Thorotrast ICC. Methylation of the hMLH1 promoter was associated with the MSI(+) phenotype in Thorotrast ICC. In contrast, methylation status of these promoter regions was not related to MSI in non-Thorotrast ICC cases. These findings suggest that MSI induced by exposure to Thorotrast mainly reflects clonal expansion of cancer cells and is partly due to inactivation of hMLH1 by hypermethylation.

A reanalysis of liver cancer incidence in Danish patients administered thorotrast using a two-mutation carcinogenesis model

In recent years, a two-mutation carcinogenesis (TMC) model has been used to analyze epidemiological data and estimate the radiation risks at low doses for the organs affected. Here the TMC model was used to reanalyze the liver cancer incidence in the Danish population in general and in patients administered Thorotrast, and to estimate the radiation risks for the liver. The data for 807 patients for whom sufficient data on the injected volumes of Thorotrast were available were used in this reanalysis. These data were combined with data on liver cancer incidence in the Danish population as the baseline or background incidence. Because males and females show different baseline liver cancer incidences, separate fits were made for males and females. The fits showed that the radiation effect could be ascribed entirely to the radiation dependence of the first mutation rate of the TMC model, which was higher for females than for males. The second mutation rate was not significantly dependent on dose. The radiation risks for the liver were calculated on the basis of the model parameters. These risks for lifetime exposures are about the same for males and females and are between a factor of 2 and 10 higher than current estimates. The discrepancy between the model results and previous risk estimates probably arises because the model calculations give more complete lifetime radiation risk estimates. For short-term exposures of the liver to ionizing radiation, the maximum radiation-induced excess liver cancer risk per unit dose applies to exposures at the age of about 10; exposures at ages above 35 have a radiation effect of less than approximately 15% of this maximum.

Cancer incidence among Swedish patients exposed to radioactive thorotrast: a forty-year follow-up survey

Thorotrast is an alpha-particle-emitting radiological contrast medium that caused chronic exposure to internal alpha-particle radiation when it was administered systemically. Cancer incidence in 432 Swedish patients exposed to Thorotrast was evaluated by computerized linkage of the cohort with the Swedish Cancer Register. Standardized incidence ratios (SIRs) were calculated as the ratio of observed cases in the cohort to expected cases in the general population. A total of 170 cancers occurring in 152 individuals were reported, whereas only 57 cases were expected. The SIR was significantly increased for cancer at all sites (3.0), with the largest excesses noted for primary liver and gallbladder cancer (SIR = 39.2). Other significantly elevated risks were observed for liver cancer not specified as primary, small intestine cancer, stomach cancer, leukemia, kidney cancer, CNS tumors, and pancreatic cancer. Among women, there was a significantly increased risk for lung cancer, based on a small number. Our results show that cumulative radiation exposure is directly related to carcinogenesis in the liver and gallbladder, which is consistent with earlier findings. In addition, there may be a relationship between radiation exposure and the development of other solid tumors.

Alpha-particle carcinogenesis in Thorotrast patients: epidemiology, dosimetry, pathology, and molecular analysis

We studied the alpha-radiation risks in patients who received injections of Thorotrast, an X-ray contrast medium used in Europe, Japan, and the United States from 1930 to 1955. Thorotrast was composed of thorium dioxide (ThO2) and Th-232, a naturally occurring radionuclide. Because the physical half-life of ThO2 is 14 billion years and Thorotrast is hardly eliminated from the body, tissues in which it was deposited are irradiated by alpha-radiation for the entire lifetime of the subject. The dosimetry of Thorotrast patients is very complicated, but currently its reliability is quite high compared with other irradiated populations. The major causes of the death of Thorotrast patients are liver cancer, liver cirrhosis, leukemia, and other cancers. Three histologies of liver cancer are found: cholangiocarcinoma, hepatocellular carcinoma, and angiosarcoma. Although cholangiocarcinoma is the most frequent, angiosarcoma is characteristic of alpha-radiation. Among blood neoplasms with a higher incidence of increase than the general population, erythroleukemia and myelodysplastic syndrome were remarkable. Thorotrast patients exhaled a high concentration of radon (Rn-220), a progeny of Th-232, but no excesses of lung cancer in the patients of Japan, Germany, and Denmark were reported. Mutation analyses of p53 genes and loss of heterozygosity (LOH) studies at 17p locus were performed to characterize the genetic changes in Thorotrast-induced liver tumors. Interestingly, LOH, supposedly corresponding to large deletions was not frequent; most mutations were transitions, also seen in tumors of the general population, suggesting that genetic changes of Thorotrast-induced cancers are mainly delayed mutations, and not the result of the direct effects of radiation.

Implanted depleted uranium fragments cause soft tissue sarcomas in the muscles of rats

In this study, we determined the carcinogenicity of depleted uranium (DU) metal fragments containing 0.75% titanium in muscle tissues of rats. The results have important implications for the medical management of Gulf War veterans who were wounded with DU fragments and who retain fragments in their soft tissues. We compared the tissue reactions in rats to the carcinogenicity of a tantalum metal (Ta), as a negative foreign-body control, and to a colloidal suspension of radioactive thorium dioxide ((232)Th), Thorotrast, as a positive radioactive control. DU was surgically implanted in the thigh muscles of male Wistar rats as four squares (2.5 x 2.5 x 1.5 mm or 5.0 x 5.0 x 1.5 mm) or four pellets (2.0 x 1.0 mm diameter) per rat. Ta was similarly implanted as four squares (5.0 x 5.0 x 1.1 mm) per rat. Thorotrast was injected at two sites in the thigh muscles of each rat. Control rats had only a surgical implantation procedure. Each treatment group included 50 rats. A connective tissue capsule formed around the metal implants, but not around the Thorotrast. Radiographs demonstrated corrosion of the DU implants shortly after implantation. At later times, rarifactions in the radiographic profiles correlated with proliferative tissue responses. After lifetime observation, the incidence of soft tissue sarcomas increased significantly around the 5.0 x 5.0 mm squares of DU and the positive control, Thorotrast. A slightly increased incidence occurred in rats implanted with the 2.5 x 2.5 mm DU squares and with 5.0 x 5.0 mm squares of Ta. No tumors were seen in rats with 2.0 x 1.0 mm diameter DU pellets or in the surgical controls. These results indicate that DU fragments of sufficient size cause localized proliferative reactions and soft tissue sarcomas that can be detected with radiography in the muscles of rats.

[Unexpected diagnosis of thorotrast-induced cirrhosis]

It is presented the clinical case of a 73 year old man admitted to hospital with dyspnea and productive cough. Clinico-instrumental investigations demonstrated monolateral pleural effusion and ascites in a severe cirrhotic chronic liver failure. After evacuation of the pleural and peritoneal effusion, chest radiography showed the presence of a double accumulation of radiopaque material in left cervical region and in left paramediastinic site. Chest and abdominal CT scan showed a systemic accumulation of this material in liver, spleen and glands. The characteristics of the iperreflecting substance accumulated were compatible with that of Thorotrast. In the mean time, a prostate cancer with skeletal metastases was diagnosed. Despite therapy, the chronic liver failure causes a rapid deterioration of clinical conditions, with irreversible hepatic coma and death.

Mortality after cerebral angiography with or without radioactive Thorotrast: an international cohort of 3,143 two-year survivors

There are few studies on the long-term sequelae of radionuclides ingested or injected into the human body. Patients exposed to radioactive Thorotrast in the 1930s through the early 1950s provide a singular opportunity, since the administration of this radiographic contrast agent resulted in continuous exposure to alpha particles throughout life at a low dose rate. We evaluated cause-specific mortality among an international cohort of 3,143 patients injected during cerebral angiography with either Thorotrast (n = 1,736) or a similar but nonradioactive agent (n = 1,407) and who survived 2 or more years. Standardized mortality ratios (SMRs) for Thorotrast and comparison patients were calculated, and relative risks (RR), adjusted for population, age and sex, were obtained by multivariate statistical modeling. Most patients were followed until death, with only 94 (5.4%) of the Thorotrast patients known to be alive at the closure of the study. All-cause mortality (n = 1,599 deaths) was significantly elevated among Thorotrast subjects [RR 1.7; 95% confidence interval (CI) 1.5-1.8]. Significantly increased relative risks were found for several categories, including cancer (RR 2.8), benign and unspecified tumors (RR 1.5), benign blood diseases (RR 7.1), and benign liver disorders (RR 6.5). Nonsignificant increases were seen for respiratory disease (RR 1.4) and other types of digestive disease (RR 1.6). The relative risk due to all causes increased steadily after angiography to reach a threefold RR at 40 or more years (P < 0.001). Excess cancer deaths were observed for each decade after Thorotrast injection, even after 50 years (SMR 8.6; P < 0.05). Increasing cumulative dose of radiation was directly associated with death due to all causes combined, cancer, respiratory disease, benign liver disease, and other types of digestive disease. Our study confirms the relationship between Thorotrast and increased mortality due to cancer, benign liver disease, and benign hematological disease, and suggests a possible relationship with respiratory disorders and other types of digestive disease. The cumulative excess risk of cancer death remained high up to 50 years after injection with >20 ml Thorotrast and approached 50%.

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 exposure to alpha irradiation caused by paravascular Thorotrast deposits.

SUBJECTS AND METHODS

899 patients, who had received the radioactive contrast medium Thorotrast for angiography in the 1930s and 1940s, and 662 controls 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 ultrasonography, CT and MRI.

RESULTS

Paravascular Thorotrast deposits were detected in 245 patients. Clinical symptoms related to deposits appeared 10 to 30 years after Thorotrast administration. The severity of symptoms depended on the location and extension of granulomas and were mainly caused by fibrosis, nerve paralysis and vascular changes. Four malignant tumors adjacent to granulomas were observed (one soft tissue sarcoma in the groin, two squamous cell carcinomas of the parotid gland and one lymphoepithelial carcinoma of the nasopharynx). MRI including MRA allowed an accurate determination of tissue damage, whereas the utility of US and CT was restricted due to strong sound attenuation and streak artefacts caused by the high X-ray absorption of Thorotrast.

DISCUSSION AND CONCLUSION

Locoregional late effects of paravascular Thorotrast deposits mainly comprise radiation induced, fibrotic tissue destruction. The incidence of malignant tumors, in particular sarcomas, adjacent to deposits, however, is much lower than initially expected.

Chromosomal aberrations and hprt mutant frequencies in long-term American thorotrast survivors

PURPOSE

Patients injected with thorotrast, a radiologic contrast medium used from the 1920s to early 1950s, received chronic internal exposure to thorium-232, an alpha-emitter. Epidemiologic studies have observed markedly elevated risks of death from hepatic and hematologic cancers and extensive chromosomal damage among these patients. Few investigations have correlated multiple measures of genetic damage to determine whether these have independent induction kinetics. The distribution of chromosomal aberrations (CA) and mutant frequencies (MF) at the hypoxanthine phosphoribosyltransferase (hprt) locus was evaluated in eight long-term thorotrast survivors (mean exposure time=47.4 years) and five individuals who received a nonradioactive contrast medium during the same era.

MATERIALS AND METHODS

Peripheral blood lymphocytes were harvested from whole blood, CA were scored in 500 complete metaphases and a clonal assay was used to determine hprt MF. Symmetrical aberrations were not evaluated. Differences in frequencies and correlations between endpoints were assessed using nonparametric methods.

RESULTS

Thorotrast-exposed individuals differed from the comparison group in total number of multicentrics and centric and acentric rings (per 500 cells [median, mean +/- sd]: 11, 18.3+/-23.1 vs 2, 2.4+/-1.1, p =0.04). There was no difference between the groups on hprt MF (12.6, 15.9+/-13.5 vs 16.6, 14.0+/-8.8[ x 10(-6)]; p= 1.0). Among the exposed, hprt MF was moderately correlated with the frequency of asymmetrical chromosomal aberrations, although the association was not statistically significant.

CONCLUSION

Noting the limitations of small samples, long-term thorotrast survivors were observed to be at an increased risk for genetic damage.

Human hemangiosarcomas have a common polymorphism but no mutations in the connexin37 gene

Gap junctional intercellular communication is often impaired in cancers, and the genes which encode the connexin gap junction proteins are considered to be tumor-suppressor genes. In this study, we analyzed the presence of mutations in the connexin 37 (Cx37) gene in 22 human hepatic angiosarcomas, 6 and 4 of which were associated with exposure to vinyl chloride and Thorotrast, respectively. The other 12 samples were from patients with no history of exposure to these 2 agents. In 9 samples, a proline (ACC) to serine (ACT) amino acid change in codon 319 was detected. However, DNA from non-tumorigenic tissue of the same patients also showed this amino acid change, suggesting that this is a polymorphism rather than a mutation. Subsequent analysis of 84 DNA samples from normal donors revealed the frequencies of Pro/Pro, Pro/Ser and Ser/Ser alleles to be 65.5%, 23.8% and 10.7%, respectively, while among the group of angiosarcoma patients the corresponding figures were 59.1%, 31.8% and 9. 1%, respectively. Thus, there was no correlation between the polymorphism at codon 319 and hepatic angiosarcoma occurrence. However, among the 6 cases of vinyl chloride-associated angiosarcoma, the percentages of the polymorphic alleles were 33.3%, 66.7% and 0%, respectively. While the number of samples was too small to allow us to conclude that the Ser319 allele in Cx37 predisposes to this rare type of human cancer, it may be noted that codon 319 is located at the cytoplasmic tail of Cx37, where most regulatory sequences reside, and that it could be a site of phosphorylation for some protein kinases, which may in turn affect the function of Cx37, including intercellular communication.

Summary of entire Japanese thorotrast follow-up study: updated 1998

Updated data from two series in a cancer mortality study for a total of 412 Japanese Thorotrast patients were combined. The rate ratio for all deaths of Thorotrast patients, compared to controls, started to increase after a latent period of 20 years after injection of Thorotrast. Rate ratios for liver cancer, liver cirrhosis, leukemia and lung cancer were 35.9, 6.9, 12.5 and 2.0 times higher, respectively, than those for controls.

Mortality in the Portuguese thorotrast study

The Portuguese Thorotrast study cohort consists of a group of patients who received Thorotrast for diagnostic reasons between 1929 and 1956, and a group of similar patients who were given nonradioactive contrast agents. The cohort members were identified from medical records that contained information on reasons for the radiological investigation, type of procedure employed, and name and dose of the contrast medium used. This cohort was assembled in 1961, but its follow-up was interrupted in 1976. We have now reactivated this cohort and extended its follow-up through the end of 1996. Similar methods were used to follow up and ascertain cause of death for the Thorotrast-exposed and unexposed subjects. A total of 1931 patients who received Thorotrast systemically and 2258 unexposed subjects were initially identified from medical records. We were able to successfully follow up 58.6% (1131) of the Thorotrast patients and 45.7% (1032) of the unexposed patients. By the end of 1996, 92.2% of the Thorotrast patients and 75.2% of the unexposed patients were dead. Mortality from all causes was increased in the Thorotrast patients compared to those who were not exposed. This excess in mortality increased with time since exposure, peaking 30 years after administration of Thorotrast. The rise in overall mortality was essentially due to neoplasms [relative risk (RR) adjusted for sex, age and period = 6.04, 95% CI = 4.42-8.26], nonmalignant liver disorders (RR = 5.67, 95% CI 3.13-10.3) and nonmalignant hematological conditions (RR = 14.2, 95% CI = 2.54-79.3). The increase in mortality from neoplasms was explained mainly by increases in the risk of liver cancer (RR = 70.8, 95% CI = 19.9-251.3) and, to a much lesser extent, leukemia (RR = 15.2, 95% CI = 1. 28-181.7).

The reticuloendothelial system and macrophage-monocyte system in thorotrast patients

To evaluate the function of the reticuloendothelial system and macrophage-monocyte system, blood samples from Thorotrast patients and age-matched healthy controls were used to determine the titer of plasma antibodies to lipid A and the numbers of several lymphocyte subclasses in peripheral blood and for an autoradiographic study of peripheral blood monocytes. The titer of plasma IgM class antibodies to lipid A was significantly elevated in the Thorotrast patients. Counts of CD 11-positive lymphocytes and CD 57-positive lymphocytes, which correspond to monocytes and natural killer cells, respectively, were significantly increased in the Thorotrast patients. Autoradiography showed that alpha-particle tracks were emitted from the monocytes isolated from the peripheral blood of Thorotrast patients. Thus the depressed function of the reticuloendothelial system resulted in the activation of the macrophage-monocyte system in the Thorotrast patients.

The german thorotrast study: recent results and assessment of risks

The German Thorotrast study comprises 2,326 patients and 1,890 controls. Forty-eight Thorotrast patients and 239 controls are still alive and are invited for a follow-up examination every 2 years. In the deceased patients, the following neoplastic diseases with excess rates were registered (Thorotrast/controls): liver cancer (454/3); cancer of the bile ducts, including gallbladder (42/7); myeloid leukemia (40/7); myelodysplastic syndrome (30/4); plasmacytoma (10/2); non-Hodgkin's lymphoma (15/5); bone sarcoma (4/1); malignant peritoneal or pleural mesothelioma (9/0). Dose calculations are based on results of whole-body counting, X-ray films, and data obtained from the hospital records on the volume of Thorotrast injected. For liver cancer, the cumulative risk estimate was calculated to be 40 per 10(4) person Sv (radiation weighting factor = 20). These figures are close to the results of the Danish study and are comparable to the results of the Life Span Study of A-bomb survivors after 40 years at risk with 18 to 48 liver cancers per 10(4) person Sv. For hematopoietic malignancies, the cumulative risk was calculated to be about 7 per 10(4) person Sv (radiation weighting factor = 20). This risk estimate is lower by a factor of 10 compared to the results of the Life Span Study.

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 administered 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 controls. Of the patients in the Thorotrast group, the main causes of death were liver malignancies (79, 30.2%), liver cirrhosis (20, 7.6%), blood diseases (9, 3.4%), and cancers of the extrahepatic bile duct (5, 1.9%). Statistical analyses by the chi(2) test and estimation of the relative risk (risk ratio) showed that the incidences of these disorders were significantly higher 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 routes. Results of analyses of the 386 autopsy cases given Thorotrast intravascularly 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. The relative risks of liver malignancies, blood diseases, bone sarcomas, malignant peritoneal tumors, and hemangiosarcoma of the spleen manifested significantly higher ratios in the Thorotrast autopsy cases (ratio of proportion) than in the autopsy control cases. Histological studies of these autopsied cases revealed that Thorotrast-induced liver malignancies showed remarkable differences in the proportions of histological types of tumors from those of non-Thorotrast liver malignancies since 1975. However, in this survey, we noted a remarkable increase in the incidence of liver malignancy of multiple histological types compared to that in histological controls. Based on the results of our 1998 survey, we estimated attributable risks of Thorotrast-inducedliver malignancies and blood diseases in the life span. Results 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).

Analysis of genetic changes in intrahepatic cholangiocarcinoma induced by thorotrast

Thorotrast, a colloidal suspension of radioactive (232)ThO(2) that emits alpha particles, was used as a radiographic contrast agent in the 1930s-1950s. Several decades after injection, Thorotrast causes liver cancers, among which intrahepatic cholangiocarcinoma (ICC) is prominent. We investigated mutations of the RAS and the TP53 genes in archival sections of ICC induced by Thorotrast. Compared to ICC that was not associated with Thorotrast, the frequency of mutation of the KRAS gene was lower, while that of the TP53 gene was more than two times higher. The most common mutation of the TP53 gene was A-G transitions. Interestingly, TP53 mutations were also found in noncancerous areas of livers in which Thorotrast had been deposited. Furthermore, mutations tended to accumulate in tissues from more advanced tumors. These results suggest that deposited Thorotrast continuously damages DNA in liver cells in some way, resulting in A-G transitions of the TP53 gene. However, we have not been able to rule out the possibility that genetic insults occur indirectly in the proliferating cells adjacent to the necrosis rather than being a direct effect of alpha particles.

Lung dosimetry for thorotrast patients: implications for inhalation of radon progeny

A peculiar feature of radiation-induced carcinogenesis in German Thorotrast patients is that no excess lung cancers have been observed so far in the epidemiological follow-up study. Two possibilities have been explored here to explain the apparent discrepancy between predicted and observed bronchial tumors: (1) Bronchial doses are smaller than presently predicted; and/or (2) lung cancer risk per unit exposure in Thorotrast patients is smaller than that derived from inhalation of (222)Rn progeny. First, the mean bronchial doses computed with an updated dosimetric model for the different radiation sources are indeed substantially smaller than previous dose estimates; however, the epidemiological findings still cannot be explained in terms of bronchial doses. Second, lung cancer risk estimates based on the revised dose estimates and relative risk coefficients specifically derived from chronic indoor exposures still yield a relative risk of 1.66 for the German Thorotrast patients. This suggests that either the lung cancer risk coefficient for inhalation of radon progeny cannot be applied to Thorotrast patients because of differences in dose distributions or exposure conditions, or the current tissue weighting factor should be applied primarily to the bronchial region of the lung in the case of exposure to radon progeny.

Cancer mortality of thorotrast patients in Japan: the second series updated 1998

The 150 male patients exposed to Thorotrast who were confirmed by a 1975-1978 national survey with diagnostic X rays of 50,860 war-wounded soldiers were followed up between 1979 and 1998 (Aichi series or second series). Age-adjusted rate ratios of deaths from all causes were 3.0 times higher in Thorotrast patients compared to controls; this was statistically significant. Rate ratios for liver cancer, liver cirrhosis and leukemia were 35.0, 7.5 and 18.2, respectively.

Chromosome aberrations in bone marrow cells from Japanese patients with thorotrastosis

Exposure of bone marrow cells to alpha-particle radiation causes various types of chromosome abnormalities and hematological malignancies. We performed chromosome analysis of hematopoietic stem cells from the bone marrow of 52 Japanese patients with thorotrastosis and 21 age-matched controls. The frequency of cells with stable chromosome abnormalities was significantly higher in the patients with thorotrastosis. Further studies found 14 clonal chromosome aberrations in cells from 11 patients (21.2%); clones observed in the cells from 2 of these patients had high frequencies of chromosome abnormalities. In one case, 68 to 100% of the cells analyzed had a large partial loss in the short arm of chromosome 1 and a translocation between the short arms of chromosomes 2 and 3 [46,XY,1p-,t(2p+;3p-)]. The cells from the other patient contained a clone with partial loss of both the short and long arms of chromosome 5 (46,XX,5p-,5q-). The frequency of this clone has been constant for the last 15 years (6-24%). We also analyzed bone marrow mononuclear cells from 17 of the patients for mutations of the TP53 tumor suppressor gene (formerly known as p53). However, no mutation was found in any of the cells, including those from the 2 patients with abnormal clones. Moreover, repeated medical examinations showed no evidence of leukemia or myelodysplasia in these patients. Our study suggests that exposure of bone marrow cells to alpha-particle radiation may induce clonal chromosomal aberrations at a high frequency.

Identification of thorotrast by gamma-spectrometry and simplified autoradiography in pathological specimens

Simplified and reliable methods for identifying thorotrast are demonstrated. On gamma-ray spectrometry, as little as 0.1 g of liver tissue gives gamma-ray spectrum characteristics to the thorium decay series, despite a low net count. When conventional film for photography is kept in contact with a paraffin section of the liver for 4 months, it develops silver grains exactly corresponding to the area of granular deposition. By combining this method with clinical and pathological findings, a diagnosis of thorotrastosis can be established without the need for special instruments or materials.

[Thorotrast-induced liver cancer: results of the German thorotrast study]

AIMS

The X-ray contrast medium Thorotrast, used worldwide between 1930 to 1950 predominantly for arteriography, consisted of a colloidal solution of thorium dioxide. The radioactive thorium-232 (half-life 1.4x10(10) years) is stored lifelong in the organs of the reticulo-endothelial system after intravascular injection, causing chronic exposure to alpha radiation. The aim of the German Thorotrast study is the assessment of radiation late effects and the calculation of risk estimates.

MATERIAL AND METHODS

The German Thorotrast study started in 1968 as a cohort study and comprises 2326 Thorotrast patients and 1890 patients of a matched control group. The Thorotrast patients who were still alive at the beginning of the study were examined by X-ray plain films of the upper abdomen and of the injection site of the contrast medium as well as by whole-body counter measurements. At the beginning we offered the patients ultrasound and later on CT and MRI at regular intervals for early detection of liver cancer.

RESULTS

To date 454 primary liver cancers have been registered in the group of Thorotrast patients compared to 3 cases in the control group. With the help of modern imaging methods relatively small liver cancers were detected and could be surgically removed.

DISCUSSION

There is a correlation between the mean accumulated dose to the liver and the incidence of liver cancer. The cumulative risk for liver malignancies is about 600 diseases per 10(4) persons whose liver was exposed to 1 Gy. Also the incidence of liver cirrhosis is correlated with the mean accumulated dose to the liver.

International radiobiology archives of long-term animal studies: structure, possible uses and potential extension

Animal experiments have contributed a great deal to our information on effects and risks arising from exposure to radionuclides. This applies, in particular, to alpha-emitting radionuclides where information from man is limited to thorotrast, 224Ra and 226Ra. The late C.W. Mays was the first to suggest that animal data in conjunction with epidemiological data could allow estimates of human risks for radionuclides - predominantly from actinides - where information in man is scarce. The 'International Radiobiology Archives of Long-term Animal Studies' were created through the combined efforts of European, American and Japanese scientists and aim to safeguard the large amount of existing data on long-term animal experiments and make them available for, among others, an improved assessment of risks from alpha-emitting radionuclides. This paper summarizes the structure of the archives and reviews their present status and future plans. It also demonstrates the extensive information available in these archives on alpha-emitting radionuclides which is suitable for further analysis. Also, the structure of the animal archives could - in a slightly modified form - accommodate the epidemiological data available on 224Ra and thorotrast and, thus, facilitate a direct comparison of data from man, dogs and rodents.

p53 mutations in tumor and non-tumor tissues of thorotrast recipients: a model for cellular selection during radiation carcinogenesis in the liver

Concerns over cancer development from exposure to environmental sources of densely ionizing, high linear energy transfer (LET) radiation, such as alpha-particles from radon, is a current public health issue. The study of tumors attributable to high LET irradiation would greatly augment our insights into the biological mechanisms of carcinogenesis. Chronic low-dose-rate internal exposure to alpha-radiation from thorium dioxide deposits following intravascular administration of the radiographic contrast agent Thorotrast is known to markedly increase the risk of cancer development, especially that of hepatic angiosarcomas and cholangiocarcinomas. Although the mechanism is hypothesized to be via cellular damage, DNA being a major target, wrought by the high LET alpha-particles, the specific genes and the actual sequence of events involved in the process of transforming a normal cell into a malignant one are largely unknown. To shed some light on the molecular mechanisms of cancer development during a lifetime exposure to alpha-radiation, we analyzed the most commonly affected tumor suppressor gene in humans, p53, in 20 Thorotrast recipients who developed cancer, mostly of hepatic bile duct and blood vessel origin. Of the 20 cases, 19 were found to harbor p53 point mutations. Moreover, the accompanying non-tumor tissues from these patients also had p53 mutations, albeit at lower frequency. The distribution pattern of the point mutations was significantly different between the non-tumor and tumor tissues, with most mutations in malignant tissues located in the highly conserved domains of the p53 gene. Our results support the idea that p53 mutations are important in the genesis of Thorotrast-induced tumors but that these point mutations are a secondary outcome of genomic instability induced by the irradiation. Additionally, non-tumor cells harboring p53 mutations may gain some survival advantage in situ but mutations in the domains responsible for the formation of structural elements critical in binding DNA may be necessary for a cell to reach full malignancy.

Mortality after long-term exposure to radioactive Thorotrast: a forty-year follow-up survey in Sweden

To evaluate temporal patterns of cause-specific mortality after long-term exposure to the alpha-particle-emitting contrast medium Thorotrast, we investigated a cohort consisting of 693 Swedish patients with neurological disorders who received Thorotrast during cerebral angiography, with follow-up ending in 1993. Standardized mortality ratios (SMRs) were calculated as the ratio of observed cases in the cohort to expected cases in the general population. Persons exposed to Thorotrast had significant excesses of all causes of death (SMR = 2.8; 95% CI 2.5-3.0), with similar increases noted for men and women. The largest risks were observed for deaths from hematological causes (SMR = 16.4; n = 8), cerebrovascular diseases (SMR = 10.1; n = 18), gastrointestinal disorders including liver cirrhosis (SMR = 5.2; n = 36), and tumors (SMR = 4.7; n = 187). There was a significant decrease in SMR with time since injection for cerebrovascular and circulatory diseases, indicative of the impact of underlying neurological disorders. In contrast, the SMR increased significantly with time for tumors and gastrointestinal diseases, suggestive of a detrimental effect of cumulative radiation dose. A significant dose-response relationship was found for all causes of death and malignant tumors among all age groups, and since SMR increased with time for the latter category, this is consistent with an effect of cumulative radiation exposure on cancer development. However, the findings should be treated with caution, since selection bias may have influenced some of the results.

Thorotrast associated nodular regenerative hyperplasia of the liver

A case of nodular regenerative hyperplasia (NRH) of the liver is described in association with exposure to the radiographic contrast medium Thorotrast. This is the first case in which the pathological findings have been fully documented. It is suggested that NRH may have developed through Thorotrast induced damage to portal vein radicles.

Cervical Thorotrast granuloma: a review of the literature and a new treatment modality

Extravasation of thorium dioxide after transcervical carotid angiography has resulted in persistent open draining neck wounds. These difficult problems have remained a challenge for the treating head and neck surgeon. Neck dissection has been the mainstay of treatment in the past; however, this has been fraught with complications. The application of doxycycline sclerosis is described in the successful resolution of a large thorotrast granulomatous neck wound. A review of the literature and the management options of Thorotrast granulomas are discussed.