The purpose of this study is to compare the usual treatment with hormonal therapy medications to treatment with low-dose tamoxifen for patients with molecular low-risk early-stage breast cancer.   

This study has 2 study groups. Participants will be randomized by a computer to assign them to one of the study groups.

Group 1 will take the usual drugs used to treat this type of cancer, either anastrozole, letrozole, exemestane, or tamoxifen, 20 mg/day orally for a total of 5 years. Group 2 will take tamoxifen at a lower dose orally for a total of 5 years.

All treatments in this study are approved by the U.S. Food and Drug Administration (FDA).

Study participation also includes study visits and follow-up 6 months after starting the study and then every year for the next 10 years.