ESR1 and cancer: However, in a large retrospective analysis of 1,322 FFPE tissue blocks from 3,121 women participating in the Cancer and Leukemia Group B 93441/INT0148 trial (four cycles of doxorubicin and cyclophosphamide followed by four cycles of paclitaxel or observation), Hayes et al [46] reported that a survival benefit from the addition of paclitaxel was evident in patients with HER2-positive tumors regardless of ER status.