Introduction to Cancer Chemotherapy

Using drugs to specifically treat cancer is a relatively new development that was discovered accidentally in the 20th century. Nitrogen mustard gas was used as a chemical warfare agent during both World War I and World War II. Observation of military personnel who were exposed to mustard gas showed that they developed abnormally low white blood counts. As a result, it was thought that a drug or other agent like mustard gas, that damaged rapidly growing white blood cells, might have a similar effect on cancer cells. Currently, over 100 drugs are now used either alone or in combination with other drugs to treat cancer. Cytotoxic drugs vary widely in their chemical composition, how they are administered, their usefulness in treating specific forms of cancer, and their side effects and toxicities.

Cancer chemotherapy is used to cure cancer, to help control cancer, or to provide palliation when a specific cancer cannot be cured or controlled. Acute lymphocytic leukemia in children, Hodgkin’s disease, lymphosarcoma, and testicular cancer are examples of types of cancer that can, in some instances, be cured by using a single cytotoxic drug. In other cancers, such as Wilm’s tumor, osteogenic sarcoma, and rhabdomyosarcoma, a cure can be achieved by using several cytotoxic drugs in combination. Types of cancer that can often be controlled by chemotherapy include breast cancer, chronic lymphocytic leukemia, chronic and acute myelogenous leukemias, small cell cancer of the lung, prostatic cancer, multiple myeloma, and ovarian cancer. In some cases, the cancer can neither be cured nor controlled and cancer chemotherapy is used to palliate or relieve distressing symptoms. For example, cytotoxic drugs can be used to help patients with advanced cancer lead more comfortable lives by relieving pressure on nerves or blood vessels or preventing organ obstruction.

Chemotherapy is sometimes the first choice for treating many cancers. For example, cytotoxic drug therapy is the treatment of choice for malignancies of the bone marrow, such as leukemia, and for solid tumors, including solid tumors that have metastasized or spread to other parts of the body. Cancer chemotherapy differs significantly from either surgery or radiation because it almost always acts systemically, affecting many cells in the body. This feature of cytotoxic drugs is important because chemotherapy can reach cancer cells that may have spread to other parts of the body. However, when cytotoxic drugs attack cells that are in the process of reproducing, the drugs can’t distinguish between normal cells and cancer cells. As a result, both cancer cells and normal cells may be destroyed or damaged, leading to potentially serious side effects. Cancer chemotherapy involves a balance between destroying cancer cells in order to cure or control cancer, and sparing normal cells in order to minimize uncomfortable and sometimes toxic side effects.