Should all postmenopausal patients with hormone receptor-positive breast cancer receive initial therapy with aromatase inhibitors?

BACKGROUND: In the past few years aromatase inhibitors (AIs) have shown superior efficacy to the previous standard adjuvant endocrine therapy, tamoxifen, and are now recommended as part of current adjuvant endocrine therapy. A range of treatment strategies have been explored. MATERIALS AND METHODS: We assess the role of initial AI therapy for postmenopausal women with hormone receptor-positive breast cancer and consider the relative value of initial therapy with an AI compared with switch or extended (>5-yr) adjuvant therapy. RESULTS: Both initial AI therapy and switching/sequential tamoxifen followed by an AI are associated with longer disease- and relapse-free survival versus 5 years of tamoxifen alone. Trials comparing initial therapy with the sequence of tamoxifen followed by an AI have not demonstrated any major efficacy differences between the treatment strategies. Several analyses have been conducted to identify prognostic or predictive markers of treatment benefit to enable selection of the most appropriate adjuvant therapy. CONCLUSIONS: Initial and switching/sequential regimens are equally appropriate adjuvant treatment options for postmenopausal patients with hormone receptor-positive breast cancer. The exact tumour biology which allows for initial AI therapy has not yet been determined with certainty.