Start strong or switch? Adjuvant endocrine strategies for postmenopausal women with hormone-sensitive breast cancer

Women are at considerable risk of recurrence in the first few years following initial treatment for early breast cancer. To reduce the risk of recurrence, including distant metastases, those with hormone-sensitive breast cancer receive adjuvant endocrine treatment. Lymph node metastases are a predictor of high risk of early recurrence and distant metastases; however, a significant number of women with node-negative disease will also develop distant metastases. This is of concern, because the development of distant metastases is associated with a high risk of breast cancer death. Studies in postmenopausal women showed that an aromatase inhibitor (AI) as initial, upfront treatment reduces early recurrence, including distant metastases, compared with tamoxifen. The three available AIs (letrozole, anastrozole, and exemestane) are approved for adjuvant use. Upfront letrozole or anastrozole improved time to distant metastasis in patients included in the Breast International Group 1-98 and Arimidex, Tamoxifen, Alone or in Combination trials, respectively. Of note, the beneficial effects of letrozole on distant disease were already observed in the first report at 2 years of follow-up and confirmed in the updated results with 50 months of follow-up. Here, we discuss the available data for all AIs and strategies to be taken into account for patient management, with a special focus on the effects of available options on early recurrences and metastasis risk.