Mammary Cancer in Rats

Abstract

There is clearly a need for a useful, practical rat model of mammary carcinogenesis, not only to produce invasive, autochthonous tumors that can be used for screening of new agents for treatment of advanced disease, but also for evaluation of new agents for chemoprevention of breast cancer. This latter approach to the control of breast cancer has seen major clinical advances in the past few years, with the demonstration of the clinical efficacy of three agents—namely tamoxifen, raloxifene, and fenretinide—in chemoprevention of breast cancer in selected groups of women at high risk for development of disease (1–3). These experimental clinical trials in chemoprevention have been extremely costly to perform, since they have involved the administration of these drugs to thousands of women over a period of many years. It is therefore of the utmost importance to be certain that there is a strong preclinical rationale for the use of a new chemopreventive agent before it is introduced into clinical trials. We have seen the disaster that has resulted from the large clinical trials that attempted to use β-carotene to prevent cancer before there was any strong evidence that this agent was truly an effective chemopreventive agent in experimental animals. Hopefully, this same mistake will not be repeated in the future with newer agents.