Used in the treatment of HER2-positive breast cancer, particularly in patients who have already received other chemotherapy regimens. It works by inhibiting the tyrosine kinase activity of the HER2 and EGFR proteins, which are involved in tumor cell growth and survival. Often prescribed in combination with other drugs like capecitabine to enhance effectiveness. Also investigated for use in other solid tumors where HER2 or EGFR pathways are overactive. Its oral formulation allows for convenient outpatient treatment compared to intravenous therapies.