Cancer Incidence among Swedish Patients Exposed to Radioactive Thorotrast: A Forty-Year Follow-up Survey

Abstract

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.

Ionizing radiation: a risk factor for mesothelioma

“…This is also true for Thorotrast. ThO 2 exposure from Thorotrast can vary among and within the organs by a factor of *100 [70]. In addition, the particles in the colloidal suspension can aggregate, facilitating significant self-absorption [71].…”

Cholangiocarcinoma in association with Thorotrast exposure

“…Although cholangiocarcinoma is the most frequent, angiosarcoma is the second most common and is more characteristic of alpha‐radiation‐induced cancer 5. In a Swedish study of patients exposed to Thorotrast, the relative risk for development of cancer at any site was 3.0, and the relative risk for primary liver and gallbladder cancer was 39.2 1. Similarly, in a Japanese study of 241 patients, the risk of death from any cause was threefold greater and the risk of developing liver cancer was 47‐fold greater than in unexposed persons 6,7.…”

“…Thorotrast is carcinogenic because thorium is an alpha‐emitter with densely ionizing high linear energy transfer and a very long half‐life (400 years). Many malignancies have been associated with Thorotrast exposure, including primary liver and gallbladder cancers, small intestine cancer, stomach cancer, leukemia, and renal cancer 1…”

La controverse sur les effets des faibles doses de rayonnements ionisants et la relation linéaire sans seuil

“…Il a semblé, aux auteurs du rapport conjoint, impossible de discuter la radiocancérogenèse sans analyser les effets d'une irradiation avec les particules α puisqu'elles causent plus de dommages cellulaires que les électrons. Or pour les alpha, l'existence d'un seuil est indiscutable dans les enquêtes sur les peintres de cadran lumineux contaminés par le radium qui ne montrent aucune augmentation de l'incidence des ostéosarcomes pour des doses inférieures à quelques Gy (Rowland et al, 1983 ;Stebbings et al, 1984 ;Carnes et al, 1997 ;Thomas, 1995 ;Fry, 1998) et celles effectuées sur des malades qui avaient reçu des injections intraveineuses de thorotrast qui ne montrent aucune augmentation de la fréquence des cancers du foie pour des doses inférieures à 2 Gy (Van Kaick et al, 1991 ;Andersson et Storm, 1992 ;Travis et al, 2003Travis et al, , 2001Nyberg et al, 2002).…”