PIK3CA and breast cancer: In contrast, the randomized phase 2 trial comparing buparlisib plus paclitaxel versus placebo plus paclitaxel in patients with HER2-negative breast cancer was stopped early for futility, as the addition of the PI3K inhibitor failed to demonstrate a significant PFS improvement in either the overall study population or in the prespecified cohort of patients with PI3K-activated tumors [30].