PIK3CA and neoplasm: Both studies reported a significant improvement in progression-free survival in the overall population, but the benefit was predominantly recorded in tumours with activating mutations in PIK3CA or AKT1 or inactivating alterations in PTEN. 22, 23 However, deficient PTEN expression is a more frequent alteration in triple-negative breast cancer than in oestrogen receptor-positive, HER2-negative breast cancer and is associated with increased AKT pathway activation,24, 25 suggesting that the relative benefit of AKT inhibition is context dependent.