The present invention relates to a method of treatment of patients suffering from cancer and harbouring mutations of EGFR in the tumour, for instance an activating mutation of the EGFR or a mutation responsible for resistance or the emergence of acquired resistance to treatment with reversible EGFR and/or HER2 inhibitors or irreversible inhibitors such as CI-1033, EKB-569, HKI-272 or HKI-357, comprising administering an effective amount of the irreversible EGFR inhibitor BIBW2992 (1) 4-[(3-chloro-4-fluorophenyl)amino]-6-{[4-(N,N-dimethylamino)-1-oxo-2-bute- n-1-yl]amino}-7-((S)-tetrahydrofuran-3-yloxy)-quinazoline, to a person in need of such treatment, optionally in combination with the administration of a further chemotherapeutic agent, in combination with radiotherapy, radio-immunotherapy and/or tumour resection by surgery, and to the use of a BIBW 2992 (1) for preparing a pharmaceutical composition for the treatment of patients suffering from cancer and harbouring mutations of EGFR in the tumour.