Inhibition of radiogenic mammary carcinoma in rats by estriol or tamoxifen
Mammary carcinomas have been induced by 3.5 Gy whole-body gamma radiation administered at age 40 to 50 days to virgin female Sprague-Dawley rats. In 142 irradiated controls carcinoma incidence averaged 7.8% in survivors observed less than 300 days and 38.3% of those surviving longer (P less than 0.001 by t test). Mammary cancer promotion was inhibited by two methods: estriol (E3) 638 micrograms/month (2.2 microns/mo) subcutaneously for natural life span begun 2 weeks after exposure reduced cancer incidence from 76% in controls to 48% after 331 to 449 mean days observation until neoplasia was palpable (P less than 0.02 by chi-square analysis). Uterine weights were similar in control and treated groups, and were 15% to 18% greater than uteri of nonirradiated controls from other simultaneous experiments. Six monthly 638-micrograms doses of 17 alpha ethinyl estriol (EE3) reduced tumors from 88% in controls to 64% (P less than 0.05 by chi-square analysis) and delayed cancer onset (P less than 0.01-0.04 by life table analysis). Ethinyl estradiol (EE2) after 6 months' treatment similarly delayed mammary tumor development reducing incidence to 75% (NS), with a six-fold increase in nonmammary epithelial malignant tumors. Estriol administration begun between 3 days before to 5 days after radiation did not alter mammary cancer incidence in six experiments. Monthly implantation of 2.5 mg tamoxifen (4.44 microns/mo) started 2 weeks after radiation reduced mammary cancer incidence from 83% to 14% after 307 to 314 days' observation (P less than 0.001 by chi-square analysis). Treated rats had atrophic ovaries and uteri consistent with blockade of endogenous estradiol activity.
- Research Organization:
- Univ. of Nebraska Medical Center, Omaha, NE (USA)
- OSTI ID:
- 6252961
- Journal Information:
- Cancer (Philadelphia); (United States), Vol. 63:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARCINOMAS
RADIOINDUCTION
ESTRADIOL
RADIOSENSITIVITY EFFECTS
ESTRIOL
MAMMARY GLANDS
EXPERIMENTAL NEOPLASMS
GAMMA RADIATION
INHIBITION
WEIGHT
BODY
DISEASES
ELECTROMAGNETIC RADIATION
ESTRANES
ESTROGENS
GLANDS
HORMONES
HYDROXY COMPOUNDS
IONIZING RADIATIONS
NEOPLASMS
ORGANIC COMPOUNDS
ORGANS
RADIATIONS
STEROID HORMONES
STEROIDS
560152* - Radiation Effects on Animals- Animals