The disclosure relates to a method of treating gastrointestinal stromal tumors (GIST), especially GIST, which is progressing after imatinib therapy or after imatinib and sunitinib therapy, using a combination comprising (a) a c-kit inhibitor selected from imatinib, nilotinib and masitinib or a pharmaceutically acceptable salt thereof； and (b) a PI3K inhibitor selected from 2-methyl-2-[4-(3-methyl-2-oxo-8-quinolin-3-yl-2,3- dihydro-imidazo[4,5-c]quinolin-1-yl)-phenyl]-propionitrile； 5-(2,6-di-morpholin-4-yl-pyrimidin-4-yl)-4-trifluoromethyl-pyridin-2-ylamine； and (S)-pyrrolidine-1,2-dicarboxylic acid 2-amide-1-({ 4-methyl-5-[2-(2,2,2-trifluoro-1,1-dimethyl-ethyl)-pyridin-4-yl]-thiazol-2-yl} - amide) or a pharmaceutically acceptable salt thereof.
