The present invention provides a method of treating a human with cancer comprising detecting at least one mutation in a PIK3CA gene or at least one mutant protein encoded by said PIK3CA gene from at least one first sample from said human and administering to said human an effective amount of 2,4-difluoro-N-{2-(methyloxy)-5-[4-(4-pyridazinyl)-6-quinolinyl]-3-pyridinyl}benzenesulfonamide or a pharmaceutically acceptable salt thereof in a pharmaceutical composition if said at least one sample has at least one mutant PI3K protein or a mutation in the PIK3CA gene.
