1184 RADIATION BIOLOGY 



Marrow cells adjacent to radioactive bone received large doses of radia- 

 tion and humans so exposed frequently developed anemia, yet only a 

 few myeloid leukemias have been reported among them. 



LIVER 



Malignant liver-cell tumors resulting from exposure to ionizing radia- 

 tions have not been described in man or animals, but there is some evi- 

 dence that massive doses of ionizing radiations may cause endothelial 

 sarcomas in man and benign hepatomas in mice. 



Ross (1936) described an illustrative example of the consequence of 

 prolonged exposure to 7 radiation in a localized area of human liver, in 

 which a hemangioma developed subjacent to a radium needle. Metas- 

 tases were present in the lung and bone marrow. The origin of the tumor 

 was traced to branches of the portal vein. Similarly, MacMahon et al. 

 (1947) described an endothelial cell sarcoma of the liver following thoro- 

 trast injections. 



Lorenz (1950, and unpublished data) noted an increased incidence of 

 hepatomas in mice following chronic 7 irradiation. The direct relation 

 of these benign nodules to irradiation remains to be demonstrated. Au 198 

 colloid had been given to man and animals, delivering to this organ many 

 times the LD 50 total-body dose, but thus far no local tumors have been 

 produced. Liver damage with some cirrhosis was seen following Au 198 

 therapy (Hahn et al., 1951). The observations thus far are sketchy, how- 

 ever. It seems that, in man, the endothelial cells of the liver are sus- 

 ceptible to neoplasia induction by irradiation while liver cells are resist- 

 ant. Chronic exposure studies with Au 198 colloid are most desirable, 

 since this colloid selectively localizes in the Kupffer cells, exposing the 

 liver to thousands of rep without causing early death of the animal. The 

 above observations suggest the possibility of neoplasia induction from its 

 use. Radiogold colloid is currently used in the experimental therapy of 

 human cancers. (Concerning cirrhosis in animals receiving thorium, see 

 Hugenin et al., 1931.) 



Direct introduction of radium into the gallbladder will cause carcinoma 

 of this organ (Biltris, 1933). 



GASTROINTESTINAL TRACT 



Lisco et al. (1947) produced carcinoma of the colon by feeding rats with 

 radioactive yttrium. These tumors were associated with polypoid hyper- 

 plasia of the colon and ulcerative colitis. The pathogenesis of these 

 tumors deserves further study, as little is known about the etiology of the 

 common tumors of the large intestine of man, and such tumors cannot be 

 easily induced by chemical carcinogens. 



