Between March 6, 2003, and Feb 8, 2012, we recruited 2980 postmenopausal women with locally excised ER-positive or PgR-positive DCIS in 236 centres from 14 countries, and randomly assigned them to receive anastrozole (n=1471) or tamoxifen (n=1509; figure 1). This evidence concerns the gene PGR and ductal breast carcinoma in situ.