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Title: Occurrence of mammary tumors in beagls given radium-226

A total of 128 primary mammary tumors (66 of them malignant) occurred in 35 female beagles injected with {sup 226}Ra at eight dose levels ranging from 0.2 to 440 kBq/kg body mass as young adults, while a total of 156 mammary tumors (57 of them malignant) were seen in 46 female control beagles not given any radioactivity. Sixty-three of 65 control dogs and 59 of 61 dogs given {sup 226}Ra survived the minimum age for diagnosis of mammary tumors of 3.75 years. Based on the observed age-dependent tumor incidence rates in the controls and on the corresponding number of dog-years at risk, the total number of observed malignant tumors in the radium group was statistically greater than the number of expected malignant tumors (66 observed vs 34 expected, P < 0.005). There was no such difference for the benign tumors. Cox regression analysis indicated no increased risk for the first tumor occurrence in irradiated dogs. Cox regression analysis of the multivariate risk sets showed no significantly increased risk for the occurrence of benign tumors but a statistically higher risk of 1.66 with a confidence interval of 1.15-2.40 for the occurrence of malignant tumors. The increased risk was dependent on dose,more » but a dependence on the frequency of previous occurrence of mammary tumors could not be confirmed. Censoring ovariectomized dogs at time of surgery decreased the relative risks slightly but did not alter the significance. Exposure to diagnostic X rays with cumulative exposures below 0.2 Gy had no effect on tumor formation. It is unknown whether the increased risk for malignant mammary tumors was due to some initial deposition of radium in sensitive tissue, a possible irradiation of fatty mammary tissue from transient radon {yields} polonium deposition, or a general effect of the overall radium deposition on the immune system of the dogs that lowered their resistance to formation of mammary tumors. 27 refs., 5 figs., 4 tabs.« less
Authors:
; ; ; ; ;  [1]
  1. Univ. of Utah, Salt Lake City, UT (United States)
Publication Date:
OSTI Identifier:
79321
DOE Contract Number:
AC02-76EV00119; AC04-76EV01013
Resource Type:
Journal Article
Resource Relation:
Journal Name: Radiation Research; Journal Volume: 138; Journal Issue: 3; Other Information: PBD: Jun 1994
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
56 BIOLOGY AND MEDICINE, APPLIED STUDIES; RADIUM 226; DOSE-RESPONSE RELATIONSHIPS; MAMMARY GLANDS; NEOPLASMS; DISEASE INCIDENCE; RADIOINDUCTION; BEAGLES; REGRESSION ANALYSIS; YIELDS