Chemotherapy

Chemotherapy, often shortened to chemo, uses medicines to destroy cancer cells or stop them from dividing. Most chemotherapy drugs attack cells that are passing through the cell cycle, for instance by damaging DNA, starving the cell of the building blocks it needs to copy DNA, or jamming the spindle that separates chromosomes during mitosis. Cancer cells, which divide often and repair damage poorly, suffer most.

Because it travels in the bloodstream, chemotherapy is a systemic treatment that can reach cancer cells anywhere in the body, unlike surgery or radiotherapy, which act on one area. It may aim to cure, to keep a cancer under control, or to ease symptoms. It can be given before surgery to shrink a tumor (neoadjuvant) or afterward to clear remaining cells (adjuvant). Several drugs are often combined and given in cycles, with rest periods that let healthy tissue recover.

Normal cells that divide quickly, such as those in hair follicles, the lining of the mouth and gut, and the bone marrow, are also harmed. This explains common side effects such as hair loss, mouth sores, nausea, tiredness and low blood counts. Most chemotherapy is given into a vein or by mouth.