Preventive effects of letrozole in the model of premenopausal mammary carcinogenesis.

Single - agent therapy with aromatase inhibitors has no established role in premenopausal women with breast cancer. In this study, tumor suppressive effects of letrozole in the prevention of N-methyl-N-nitrosourea - induced mammary carcinogenesis in female Sprague-Dawley rats were evaluated. Letrozole was dietary administered in two concentrations - 1 mg/1 kg (LETRO 1), and 10 mg/1 kg (LETRO 10). Letrozole suppressed incidence of mammary gland cancer by 93 % (P<0.00002) in the group LETRO 1 in comparison with control animals. Total suppression of mammary carcinogenesis was observed in the group LETRO 10. In the groups with letrozole, uterine and vaginal atrophy was found at the end of experiment. In letrozole - treated animals in comparison with untreated animals, increased plasmatic triacylglycerol concentrations (P<0.0001) were observed, but total cholesterol and cholesterol of low- and high- density lipoprotein fractions were not significantly changed. An increase in body weight gain and food intake was found in the groups LETRO 1 and LETRO 10 compared with the control group (P<0.0001). The present study points to high tumor suppressive effects of letrozole in premenopausal model of mammary carcinogenesis in female rats.