SOFT-TISSUE TUMORS AMONG BEAGLES INJECTED WITH RA-226

A total of 409 primary soft-tissue tumors (189 malignant) occurred amo ng 87 of 120 young adult beagles (72.5%) injected with Ra-226 in eight dose levels ranging from 0.2-440 kBq kg(-1) body mass, while a total of 565 primary soft-tissue tumors (208 of them malignant) were seen am ong 117 of 133 control beagles not given radioactivity (88%). Because the p-value for the difference in these two percentages was > 0.05, fu rther comparisons were not made of all tumor locations or types taken together but only of the individual tumor locations or types. There wa s a clear excess of malignant turners and all tumors (benign plus mali gnant) in the eye among dogs injected with radium (p < 0.05, p < 0.01, respectively), but the occurrence of all the other types of soft-tiss ue tumors was not greater in irradiated vs. control dogs (p > 0.05). T his was also true for hematopoietic tumor types (including just one le ukemia in a control and none in irradiated dogs) in which there was no difference between controls and dogs given radium. The following tota l tumors (benign plus malignant) occurred in control dogs but not in r adium dogs: brain = 3, peritoneum = 1, and pituitary = 4. Malignant tu mors other than leukemia appearing in control animals and not among ra dium dogs were brain = 2, lymph nodes = 1, adrenal = 3, uterus = 1, an d pancreas = 5. Tumors that occurred in dogs given radium and not in c ontrols were 3 mast cell sarcomas and 2 tumors of the thymus (1 malign ant). Age at first tumor diagnosis for corresponding tumor types did n ot seem to differ (p > 0.10 or p > 0.05) between radium dogs and contr ols except for the eye (p < 0.05), with radium dogs being somewhat you nger than controls at first diagnosis, at death, or at loss from the c olony. Cox regression indicated differences between radium dogs and co ntrols in risk of dying with specific tumors. The following tumors had p values of < 0.05 and risk ratios of > 2.2:eye, mouth (mostly melano mas), and thyroid for malignant tumors and for malignant and benign tu mors together. When all sarcomas were considered as a group, there was no difference between controls and radium dogs but there was a differ ence for all carcinomas taken together, even when mammary tumors and e ye tumors were excluded and when eye tumors alone were excluded.