Progression of endocrine therapies for breast cancer: where are we headed?

Endocrine therapy remains a key part of the management of patients with hormone receptor-positive breast cancer. Tamoxifen has been the gold standard for 25 years and remains a very effective treatment. The third generation aromatase inhibitors (anastrozole, letrozole and exemestane), however, have shown slightly greater efficacy in both metastatic and early breast cancer with a different side-effect profile and no major toxicities identified to date. In premenopausal women, the role of ovarian suppression is being assessed in addition to other therapies. Experimental studies suggest synergy between endocrine therapy and signal transduction inhibitors, and these are being explored in clinical trials. A key question for all forms of endocrine therapy remains optimal duration. Evidence is emerging to suggest that, for some women, treatment should be continued for many years and perhaps lifelong.