Estrogenic Recruitment Followed by Chemotherapy in Breast Cancer: Experimental and Clinical Results

In the last decade the chemotherapy of metastatic breast cancer has reached a plateau in terms of response rate and survival [1]. The knowledge of hormone dependency of at least a proportion of breast tumors has stimulated investigation into the possibility of improving results by combining chemo-hormonotherapy. Unfortunately many randomized clinical trials fail to demonstrate any clear advantage of such combinations [2]. One reason for this lack of potentiation could be due to the fact that tamoxifen drives cancer cells into a resting state that is a kinetic sanctuary from cytotoxic agents. On the other hand, a large amount of experimental data* has demonstrated that low levels of estrogens are able to induce kinetic recruitment of breast cancer cells [3]. Therefore, the new era of clinical studies are based on a more rational approach: estrogens are given to stimulate tumor growth so that subsequent chemotherapy can act on a larger proportion of cycling cells.