DeCensi A, et al. - While tamoxifen is effective when administered for 5 years at 20 mg/d in breast cancer treatment and prevention, toxicity limits its broad use. In addition, the Biomarker trials indicated the non-inferiority of 5 mg/d vs 20 mg/d in reducing breast cancer proliferation, so researchers tested if a lower dose given for a shorter period can prevent recurrence from breast intraepithelial neoplasia with a lower toxicity vs the standard dose. In this multicenter randomized trial, 500 women (75 years of age or younger) with hormone-sensitive or unknown breast intraepithelial neoplasia, including atypical ductal hyperplasia and lobular or ductal carcinoma in situ were included. These women were randomized to receive tamoxifen, 5 mg/d or placebo for 3 years after surgery. Outcomes suggest the efficacy of tamoxifen at 5 mg/d for 3 years for reducing the recurrence of breast intraepithelial neoplasia by half, with limited toxicity, providing a new treatment option in these patients.