(2Z)-Afatinib is primarily used in the treatment of non-small cell lung cancer (NSCLC), particularly in cases where the cancer cells have specific mutations in the EGFR (epidermal growth factor receptor) gene. It works by inhibiting the activity of these mutated EGFR proteins, which are often responsible for the uncontrolled growth of cancer cells. This targeted approach helps to slow down or stop the progression of the disease, providing a more effective treatment option compared to traditional chemotherapy. Additionally, it is sometimes used in other types of cancers where EGFR mutations are present, offering a personalized treatment strategy based on the genetic profile of the tumor.