After surgery and other treatments, women diagnosed with early-stage, hormone-receptor-positive breast cancer usually take some type of hormonal therapy medicine to lower the risk of recurrence (the cancer coming back). Tamoxifen is the hormonal therapy medicine that has been approved the longest and is approved to treat both premenopausal and postmenopausal women. Research has shown that taking tamoxifen for 10 years instead of 5 offers more benefits, so many women are now taking tamoxifen for 10 years. The other main type of hormonal therapy medicines are aromatase inhibitors, which are approved to treat only postmenopausal women. Most women take an aromatase inhibitor for 5 years.