The NSABP (National Surgical Adjuvant Breast and Bowel Project) B-24 study evaluated the effect of five years of adjuvant tamoxifen in patients with DCIS treated with lumpectomy and radiation [45,46]; a subsequent analysis of 732 cases with complete hormone receptor information, report estrogen receptor (ER) was positive in 76% of patients. Here, ESR1 is linked to ductal breast carcinoma in situ.