This study is being done to answer the following question: Is treatment with a lower dose of tamoxifen, a form of hormonal therapy, as good as the usual hormonal therapy in women with low-risk, early-stage breast cancer? The usual approach for patients who are not in a study is treatment with hormonal therapy. Hormonal therapy can be an aromatase inhibitor (such as letrozole, anastrozole, or exemestane) or tamoxifen at a dose of 20mg/day. Your doctor can explain which treatment may be best for you. For patients who get the usual approach for this cancer, about 96 out of 100 are free of cancer...