Shifting paradigms in hormonal therapy for breast cancer

Background: Tamoxifen has been the mainstay of endocrine treatment for postmenopausal patients with early and advanced breast cancer for many years. However, as an anti-estrogen with partial estrogenic effects, tamoxifen also has some serious safety and tolerability issues. Following tamoxifen treatment failure there were initially limited options for subsequent therapy. Therefore, new agents, including new anti-estrogens and aromatase inhibitors (Als) were developed. Methods: Data for this review were identified by searches of PubMed and references from relevant articles. Abstracts were included only when the relevant information had not been published in full elsewhere. Only papers published in English were included. Results: The Als have been shown to be effective treatments for hormone-sensitive metastatic breast cancer. Conclusions: Current clinical trial data in early breast cancer show longer disease-free survival and time to recurrence with onastrozole than that demonstrated with tamoxifen and very good general tolerability, although longer follow-up is warranted. Clinical trials of the use of Als in breast cancer prevention and preliminary data for the combination of anastrozole with a gonadotrophin-releasing hormone for the treatment of premenopausal women with early stage breast cancer are also discussed here.