A total of 409 primary soft-tissue
tumors (189 malignant) occurred among 87 of 120 young adult beagles (72.5%) injected with 226Ra 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 among 117 of 133 control beagles not given radioactivity (88%). Because the p-value for the difference in these two percentages was > 0.05, further comparisons were not made of all
tumor locations or types taken together but only of the individual
tumor locations or types. There was a clear excess of malignant
tumors and all
tumors (benign plus malignant) 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-tissue
tumors was not greater in irradiated vs. control dogs (p > 0.05). This was also true for hematopoietic
tumor types (including just one
leukemia in a control and none in irradiated dogs) in which there was no difference between controls and dogs given
radium. The following total
tumors (benign plus malignant) occurred in control dogs but not in
radium dogs: brain = 3, peritoneum = 1, and pituitary = 4. Malignant
tumors other than
leukemia appearing in control animals and not among
radium dogs were brain = 2, lymph nodes = 1, adrenal = 3, uterus = 1, and pancreas = 5.
Tumors that occurred in dogs given
radium and not in controls were 3
mast cell sarcomas and 2
tumors of the thymus (1 malignant). Age at first
tumor diagnosis for corresponding
tumor types did not seem to differ (p > 0.10 or p > 0.05) between
radium dogs and controls except for the eye (p < 0.05), with
radium dogs being somewhat younger than controls at first diagnosis, at death, or at loss from the colony. Cox regression indicated differences between
radium dogs and controls 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
melanomas), and thyroid for malignant
tumors and for malignant and benign
tumors together. When all
sarcomas were considered as a group, there was no difference between controls and
radium dogs but there was a difference for all
carcinomas taken together, even when mammary
tumors and eye
tumors were excluded and when eye
tumors alone were excluded.