Etoposide is primarily used as a chemotherapy agent in the treatment of various types of cancer. It is especially effective in treating testicular cancer and small cell lung cancer. It is also used in the management of lymphomas, leukemias, and certain tumors in pediatric and adult patients. Etoposide works by inhibiting the action of topoisomerase II, an enzyme involved in DNA replication and repair, leading to DNA strand breaks and ultimately cancer cell death. It is often used in combination with other chemotherapeutic drugs to enhance its effectiveness. The drug can be administered orally or intravenously, depending on the treatment regimen. Due to its mechanism of action, etoposide is cell-cycle specific, mainly targeting cells in the S and G2 phases, making it particularly potent against rapidly dividing cancer cells.