Afatinib is a medication used primarily to treat certain types of lung cancer, specifically non-small cell lung cancer (NSCLC) that is positive for the EGFR mutation. It works by inhibiting the activity of the epidermal growth factor receptor, which helps to slow down or stop the growth of cancer cells. This drug is taken orally and is often prescribed for patients whose cancer has progressed after other treatments. Common side effects may include diarrhea, rash, and mouth sores. Regular monitoring by healthcare professionals is essential to manage these effects and assess the treatment's effectiveness.