PIK3CA and breast cancer: Another randomized, phase III clinical trial, BELLE‐2 (NCT01610284), was designed to assess the efficacy of the PI3K inhibitor, buparlisib, plus fulvestrant.50 Postmenopausal women (aged >18 years) with histologically confirmed HR+ and HER2− inoperable locally advanced or metastatic BC with disease progression on or after AI treatment were included.