PIK3CA and breast cancer: A phase II trial using taselisib (GDC-0032) and tamoxifen is currently underway (Baird et al., 2019), and the recently completed randomized phase III SOLAR-1 clinical trial demonstrated a clinically relevant benefit if endocrine therapy (fulvestrant) was combined with a PI3Kα inhibitor (BYL-719) in patients with HR+ HER2-advanced breast cancer with PIK3CA mutations (André et al., 2019).