Methods are provided of treating a human for cancer comprising administering at least one dose of lapatinib, or a pharmaceutically acceptable salt or composition thereof, to a patient, wherein said patient does not have one or more allelic polymorphisms selected from the group of: HLA-DQA1*0201, HLA-DQB1*0202, and HLA-DRB1*0701. Patients may also be free of genotypes in TNXB; rs12153855 and/or rs17207923.