Endocrine management of breast cancer

Hormonal therapy for breast cancer began more than a century ago with the observation that bilateral oophorectomy caused tumor regression in selected premenopausal patients. In the first half of this century, besides extending ablation of ovarian function to photon irradiation, surgical adrenalectomy and hyophysectomy were introduced, and hormonal additive therapy was established. Regression rates for advanced breast cancer with all types of endocrine therapy at this point did not exceed 35%. The demonstration that adjuvant systemic therapy can prolong the disease-free interval and improve overall survival has been a major advance in the management of breast cancer, the rationale was to control or eliminate micrometastases before tumor recurrence. The nonsteroidal antiestrogen tamoxifen was chosen for the majority of studies since the mid-1970s. Since the first report of successful treatment of metastatic breast cancer, the number of treated women worldwide has reached over 3,000,000. Objective response rate (CR+PR following UICC) in unselected patients is 34%. Tamoxifen has been used successfully to treat both pre- and postmenopausal women with all stages of the disease. In an overview analysis of 30,000 patients from 40 trials of adjuvant tamoxifen, a significant increase was found in both disease-free and overall survival. When patients were separated by nodal status, statistically significant increases were observed in disease-free and overall survival for both node-positive and node-negative patients. Women over 50 appear to benefit most from tamoxifen treatment experiencing highly significant increases in disease-free and overall survival regardless of nodal status. However, since tamoxifen primarily acts as a cytostatic and not cytotoxic agent, most patients ultimately experience disease recurrence or progression during or after therapy. Newer antiestrogens include trioxifene, toremifene, and droloxifene (3-OH-tamoxifen). Randomized, prospective studies are still under way to establish their clinical superiority (or lack of it). Progestins exert direct antiproliferative effects on human breast cancer cell lines. They may also exert direct antiestrogenic action by increasing the oxidative activity of 17 beta-hydroxy-steroid-dehydrogenase, thereby facilitating the conversion of estradiol to estrone. Progestins may exert additional antiestrogenic effects by suppressing estrogen receptor levels. As they also cause estrogen deprivation indirectly through suppression of pituitary ACTH secretion, resulting in reduced production of adrenal androgen precursors, both low- and high-dose regimens have been studied. Aromatase inhibition in premenopausal women interrupts estrogen biosynthesis; the reflex rise in FSH then stimulates production of new aromatase enzyme, and the LH increment results in enhanced ovarian steroidogenesis, counteracting the inhibitory action of aromatase-blocking drugs on the ovary.(ABSTRACT TRUNCATED AT 400 WORDS)