Chemotherapy is a type of cancer treatment that uses drugs to kill cancer cells. The drugs work by targeting the rapidly dividing cells of the cancer, but can also damage healthy cells in the process. The drugs can be administered orally, intravenously, or topically, depending on the type of cancer and the individual patient. Chemotherapy can help to reduce the size of a tumor, eliminate cancer cells, and reduce the risk of cancer spreading to other parts of the body.