By contrast, patients with ovarian cancer and simultaneously occurring KRAS or BRAF mutations achieved a partial response with these inhibitors, thereby indicating that the RAS/RAF/MEK pathway serves as a driver of resistance to PI3K inhibitors and suggesting that screening for PI3KCA (and RAS or RAF) could be used to predict PI3K/AKT/mTOR response clinically. This evidence concerns the gene PIK3CA and ovarian carcinoma.