Chemotherapy is a treatment of cancer with drugs (or medication). A chemotherapy drug acts by killing tumor cells. When chemotherapy is delivered, either in the form of an injection or an oral medication, the drug travels through the blood to reach the tumor. There it can act on tumor cells in many ways, ultimately causing their death.
Cancer cells are not like bacteria or other microbes. They are the body's own cells modified by gene changes to become a cancer. In the process of killing cancer cells, chemotherapy drugs should not result in a lot of damage to the other normal cells of the body. Most of the side effects of chemotherapy result from small amounts of damage to normal cells with the drugs used.
Usually a combination of drugs is used in chemotherapy. Each has its own way of causing cancer cell damage. This can improve the effect on cancer cells. It also lets less of each drug be used, thus reducing the possibility of side effects.
