Actuarial analysis of the hazard for mammary carcinogenesis in different rat strains after X- and neutron irradiation
article
Mammary carcinogenesis in three different rat strains has been studied after single and fractionated irradiations with X-ray and monoenergetic neutrons of three energies. The aims of the programme are the investigation of the nature of the dose-effect relationships, and the determination of the relative biological effectiveness (RBE) of neutrons. Histopathological examinations of tumours has been completed and dose-effect relations are reported separately for the induction of benign and malignant lesions. Appropriate corrections have been made for competing risks in the tumour rate analysis. The probability curves for survival without evidence of tumours have been described by Weibull distributions. This continuous parameteric failure-time model is used to derive the relative excess hazard for exposure to X-rays and neutrons. The different rat strains show considerable differences in susceptibility for the induction of cancer by radiation. In general linear dose-response curves have been observed for mammary tumourigenesis in the three rat strains for both X-rays and fast neutrons. Within the statistical precision of the data a dependence of the RBE on neutron dose cannot be recognised. The highest RBE values, varying between 7 and 15 for different types of tumours in the three rat strains have been observed for 0.5 MeV neutrons. These RBE values are lower in general than those observed by other groups for beams of comparable energy.
Topics
animal experimentanimal modelbreastbreast cancercontrolled studydose responsedrug responsehistologyhistopathologyneutron radiationnonhumanradiation carcinogenesisrelative biologic effectivenesstheoretical studyX rayAdenofibromaAnimalCarcinomaDose-Response Relationship, RadiationFemaleMammary Neoplasms, ExperimentalNeoplasms, Radiation-InducedNeutronsProbabilityRatsRats, Inbred StrainsSupport, Non-U.S. Gov'tTime FactorsX-Rays
TNO Identifier
230077
ISSN
01452126
Source
Leukemia Research, 10(7), pp. 749-754.
Pages
749-754
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