In patients with PI3K pathway-activated breast cancers (n = 372), median PFS was 6.8 months (95% CI 4.9–7.1) in the buparlisib group versus 4.0 months (3.1–5.2) in the placebo group (HR 0.76 (0.60–0.97), one-sided p = 0.014). This evidence concerns the gene PIK3CD and breast cancer.