To further assess the role of PIK3CA mutations in breast cancer, a mutational analysis of PIK3CA/AKT1 and RAS/RAF was performed on 4,294 primary tumor samples from postmenopausal patients with ER+ breast cancer who had been enrolled in the Tamoxifen Exemestane Adjuvant Multinational phase III trial [29]. Here, ESR1 is linked to breast cancer.