chemotherapy /-ther″əpē/ , the treatment of cancer, infections, and other diseases such as cancer with chemical agents. The term has been applied over the centuries to a variety of therapies, including malaria therapy with herbs and use of mercury for syphilis. In modern usage, chemotherapy usually entails the use of chemicals to destroy cancer cells on a selective basis. The cytotoxic agents used in cancer treatments generally function in the same manner as ionizing radiation; they do not kill the cancer cells directly but instead impair their ability to replicate. Most of the commonly used anticancer drugs act by interfering with deoxyribonucleic acid and ribonucleic acid activities associated with cell division. Chemotherapeutic agents are often used in combination to intercept cell replication at various points of the cell cycle. These agents are also often used in combination with other cancer treatments such as radiation therapy and targeted therapy for their synergistic effect. For example, a cytotoxic agent may be used to render a tumor cell more sensitive to the effects of ionizing radiation, thus allowing the cancer to be controlled with smaller doses of radiation. Chemotherapy is not selective; it kills healthy cells as well as cancer cells. −chemotherapeutic, adj.
