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Mammary tumor occurrence in beagles given 239Pu
R D Lloyd1, F W Bruenger, W Angus
1Radiobiology Laboratory, University of Utah, Salt Lake City 84112, USA.
Health Physics
|September 1, 1995
Summary
Plutonium-239 (Pu) exposure did not increase mammary tumor risk in female beagles. This study found no significant differences in benign or malignant mammary tumors between Pu-exposed dogs and controls, suggesting alpha irradiation alone may not drive these cancers.
Area of Science:
- Radiobiology
- Oncology
- Toxicology
Background:
- Internalized radionuclides pose risks for cancer development, particularly alpha-emitters like Plutonium-239 (Pu).
- Mammary tumors are a common concern in canine models, and understanding radionuclide effects is crucial for risk assessment.
- Previous studies indicated potential differences in mammary cancer occurrence between dogs exposed to 226Ra and controls.
Purpose of the Study:
- To investigate the potential link between intravenous Plutonium-239 (Pu) exposure and the incidence of mammary tumors in female beagles.
- To compare mammary tumor risk and survival age at diagnosis between Pu-exposed beagles and a control group.
- To evaluate the role of alpha irradiation from skeletal deposition versus other mechanisms in mammary carcinogenesis.
Main Methods:
- A cohort of 120 young adult female beagles received intravenous injections of Plutonium-239 (Pu) at doses ranging from 0.026 to 106 kBq/kg.
- A comparable group of 63 female beagles served as controls.
- Mammary tumor incidence (benign, malignant, and all types) and survival age at diagnosis were analyzed using Chi-square and Kaplan-Meier methods.
Main Results:
- No statistically significant differences were observed in the risk of benign, malignant, or overall mammary tumors between Pu-exposed beagles and controls (p > 0.05).
- Observed tumor counts were comparable to expected values, with no significant increase in malignancy rates in the Pu-exposed group.
- Kaplan-Meier analysis showed no significant difference in survival age at the first mammary tumor diagnosis between the groups (11.75 years for Pu vs. 11.90 years for controls).
Conclusions:
- Intravenous administration of Plutonium-239 (Pu) did not elevate the risk of mammary tumors in young adult female beagles.
- These findings suggest that alpha irradiation from skeletal deposition of Pu may not be a primary driver of mammary carcinogenesis.
- The results support the hypothesis that other factors, potentially related to the radionuclide's progeny or initial deposition site, influence mammary cancer development, as suggested by prior 226Ra studies.