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Definition of Chemotherapy

Chemotherapy: 1. In the original sense, a chemical that binds to and specifically kills microbes or tumor cells. The term chemotherapy was coined in this regard by Paul Ehrlich (1854-1915).
2. In oncology, drug therapy for cancer. Also called "chemo" for short.

Most cancer chemotherapeutic drugs are given IV (into a vein) or IM (into muscle). Some anticancer agents are taken orally (by mouth). Chemotherapy is usually systemic treatment, meaning that the drugs flow through the bloodstream to nearly every part of the body.

Patients who need many rounds of IV chemotherapy may receive the drugs through a catheter (a thin flexible tube). One end of the catheter is placed in a large vein in the chest. The other end is outside the body or attached to a small device just under the skin. Anticancer drugs are given through the catheter.

Chemotherapy is generally given in cycles: a treatment period is followed by a recovery period, then another treatment period, and so on. Usually a patient has chemotherapy as an outpatient at the hospital, at a doctor's office or clinic, or at home. However, depending on which drugs are given and the patient's general health, the patient may need to stay in the hospital for a short time.

The side effects of chemotherapy depend mainly on the drugs and the doses the patient receives. Most anticancer drugs affect cells that divide rapidly. These include blood cells, which fight infection, help the blood to clot, or carry oxygen to all parts of the body. When blood cells are affected by anticancer drugs, patients are more likely to develop infections, may bruise or bleed easily, and may have less energy. Cells that line the digestive tract also divide rapidly. As a result of chemotherapy, patients can have side effects, such as loss of appetite, nausea and vomiting, hair loss, or mouth sores. For some patients, medicines can be prescribed to help with side effects, especially with nausea and vomiting. These side effects tend to gradually go away during the recovery period or after treatment stops.

Hair loss, another side effect of chemotherapy, is a major concern for many patients. Some chemotherapy drugs only cause the hair to thin out, while others may result in the loss of all body hair. Patients may feel better if they decide how to handle hair loss before starting treatment.

In some men and women, chemotherapy drugs cause changes that may result in a loss of fertility (the ability to have children). Loss of fertility can be temporary or permanent depending on the drugs used and the patient's age. For men, sperm banking before treatment may be a choice. Women's menstrual periods may stop and they may have hot flashes and vaginal dryness. Periods are more likely to return in young women.

In some cases, bone marrow transplantation and peripheral stem cell support are used to replace blood cell production when it has been destroyed by chemotherapy and/or radiation therapy.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=2698
Last Editorial Review: 8/28/2013

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