Lapatinib ditosylate is primarily used in the treatment of certain types of breast cancer, particularly those that are HER2-positive. It works by inhibiting the tyrosine kinase activity of the HER2/neu and EGFR receptors, which are often overexpressed in these cancers, thereby slowing down or stopping the growth of cancer cells. This medication is typically administered in combination with other chemotherapy agents, such as capecitabine, to enhance its efficacy. It is especially beneficial for patients who have not responded adequately to other treatments like trastuzumab. Lapatinib ditosylate is also being investigated for its potential use in other cancers where HER2 signaling plays a crucial role, offering hope for expanded therapeutic applications in the future.