Current topics and perspectives on the use of aromatase inhibitors in the treatment of breast cancer

Tamoxifen has played a central role in endocrine therapy for hormone-responsive breast cancer. Results of recent clinical trials have, however, clearly shown that third-generation aromatase inhibitors (AIs), such as anastrozole, letrozole and exemestane, are superior to tamoxifen in the treatment of postmenopausal patients with metastatic breast cancer, in an adjuvant setting and for early breast cancer. Many studies have been published that describe new results from clinical trials and how they fundamentally prove the efficacy of AIs. There are, however, still some unresolved issues concerning the applications of AIs, such as the optimal duration of the therapy, the optimal regimens (initial, adjuvant or switching from tamoxifen to AI), and combination with LH–RH agonists for premenopausal woman. These issues are discussed in this review. Additionally, further possibilities for the application of AIs, for example in combination therapy with pure antiestrogen aimed at complete estrogen blockade and in combination with new biological agents, as well as the pharmacogenomics of AIs will be discussed.