Endocrine therapy of breast cancer. Status and perspectives

Abstract

The modified therapeutic approach to metastatic breast cancer has been influenced by the realization that it cannot be cured even with the most aggressive chemotherapy. Consequently, quality of life and duration of remission have become more important parameters than judging therapeutic success only by rate of remission. The discovery of hormone receptors and of potent drugs with few side effects, which replaced ablative procedures, has led to an increased significance of endocrine therapy. Improved understanding of the endocrine mechanisms regulating malignant growth and their relationship to growth factors and tumor associated proteolysis have concurrently stimulated clinical research. Endocrine manipulation of malignant growth is based on competitive (antihormones), inhibitive (aromatase inhibitors, LHRH agonists), additive (gestagens) and ablative (ovarectomy) mechanisms. The knowledge of the optimal sequence and modality is mandatory for an individualized treatment, leading to significant advantages for the majority of patients. Premature induction of cytotoxic polychemotherapy may even cause disadvantages for subgroups of patients and should only be used as primary therapy in those situations, where urgent remission is mandatory. Only after all endocrine therapies have been tried and evaluated, one should turn to chemotherapy, whereby a trend towards "soft" chemotherapy, often as monotherapy, is favoured. The development of new substances, such as long acting LHRH analogues, "pure" antiestrogens with high receptor affinity, highly potent selective aromatase inhibitors and also the discovery of anti-progestins lead to further improvement of endocrine therapy in relation to efficacy as well as reduction of side effects. Adjuvant endocrine therapy with Tamoxifen correlates positively with the course of the disease and the survival rate in postmenopausal women. Unfortunately no effective adjuvant hormone therapy in premenopausal women exists to date.