New developments in the treatment of postmenopausal breast cancer.

In recent years, new agents have challenged tamoxifen as the standard endocrine therapy for postmenopausal breast cancer. This article reviews developments with regard to the third-generation aromatase inhibitors (AIs)--anastrozole, letrozole and exemestane--and fulvestrant, the first of a new type of estrogen receptor antagonist that, unlike tamoxifen, has no partial agonist activity. The final results of the "Arimidex", Tamoxifen, Alone or in Combination (ATAC) trial, at a median follow-up of more than five years, and recent results from switching studies with anastrozole and exemestane, strengthen the position of these AIs as adjuvant treatment for hormone receptor-positive early breast cancer. Sequencing options for the future are also discussed because non-steroidal AIs are increasingly used early in the treatment sequence.