The invention is directed, in part, to selective cancer treatment regimes based on assaying for the presence or absence of a mutation in PI3K in a blood or serum sample obtained from a patient having cancer. The cancer is treated with 5-(2,6-di-morpholin-4-yl- pyrimidin-4-yl)-4-trifluoromethyl-pyridin-2-ylamine or its hydrochloride salt, or (S)-Pyrrolidine-l,2-dicarboxylic acid 2-amide l-({4-methyl-5- [2-(2,2,2-trifluoro-l,l-dimethyl-ethyl)-pyridin-4-yl]-thiazol-2-yl}- amide).
