PIK3CA and gastrointestinal stromal tumor: Patients treated with imatinib for gastrointestinal stromal tumor (GIST) with c-KIT mutations in exon 11 have an 83.5% response rate versus 47.8% in patients with exon 9 mutations [16], and PIK3CA H1047R mutations may be more sensitive to PI3K/Akt/mTor inhibitors than other PIK3CA mutations [11].