The present invention provides a method of treating breast cancer that is nonresponsive to treatment with trastuzumab, comprising administering to a subject in need of such treatment a therapeutically effective amount of compound N-(3,4-dichloro-2-fluorophenyl)-7-({[(3aR,6aS)-2-methyloctahydrocyclopenta[c]pyrrol-5-yl]methyl}oxy)-6-(methyloxy)quinazolin-4-amine, or a pharmaceutically acceptable salt thereof.