Chemotherapy is treatment of a disease or medical condition with chemicals that attack the cause of the medical condition. The term is most commonly usedto describe treatment of cancer with anticancer drugs. Chemotherapy destroyscancer cells in a tumor. It can also kill cancer cells that have broken off from the main tumor and traveled through the blood or lymph systems to spread(metastasize) to other parts of the body.
Scientists have explored the use of chemicals to treat cancer since the mid-nineteenth century. The sex hormones estrogen and androgen were first used totreat breast and prostate cancer in 1945, and a year later, the first chemotherapy drug developed specifically to treat cancer was introduced by Americanscientist Cornelius Rhoads.
Today, more than 50 chemotherapy drugs are available to treat cancer and manymore are under development. Most chemotherapy drugs interfere with the ability of cells to grow or multiply. They are classified based on how they work.The main types of chemotherapy drugs are alkylating drugs, antimetabolites, antitumor antibiotics, plant alkaloids, and steroid hormones.
Many chemotherapy drugs fight cancer by interfering with DNA, the molecule that encodes, or maps, genetic information in the body. Alkylating drugs (suchas cyclophosphamide) kill cancer cells by directly attacking DNA. Antimetabolites (such as 5-fluorouracil) interfere with the production of DNA and keep cells from growing and multiplying. Antitumor interfere with production of DNAand cell proteins. They are made from natural substances such as fungi. Doxorubicin and bleomycin belong to this group of chemotherapy drugs.
Plant alkaloids slow cancer growth by preventing cells from dividing. Vinblastine and vincristine are plant alkaloids obtained from the periwinkle plant.Steroid hormones slow the growth of some cancers that depend on hormones. Forexample, tamoxifen is used to treat breast cancers that depend on the hormone estrogen for growth.
Chemotherapy can cure some types of cancer. In some cases, it is used to slowthe growth of cancer cells or to keep the cancer from spreading to other parts of the body. Chemotherapy can also ease the symptoms of cancer, helping some patients to have a better quality of life. Chemotherapy is usually given in addition to other cancer treatments, such as surgery and radiation therapy.When given with other treatments, it is called adjuvant chemotherapy.
Oncologists, doctors who specialize in treating cancer, determine which chemotherapy drugs are best suited for each patient. This decision is based on thetype of cancer, the patient's age and health, and other drugs the patient istaking. Some patients should not be treated with certain chemotherapy drugs.Age and medical conditions such as heart disease, kidney disease, and diabetes may affect the drugs with which a person may be treated.
How often and how long chemotherapy is given depends on the type of cancer, how patients respond to the drugs, patients' health and ability to tolerate the drugs, and on the types of drugs given. An oncologist decides which chemotherapy drug or combination of drugs will work best for each patient. The use of two or more drugs together often works better than a single drug for treating cancer. This is called combination chemotherapy.
Chemotherapy drugs are administered in different ways, depending on the drugsto be given and the type of cancer. Oral chemotherapy is given by mouth in the form a pill, capsule, or liquid. Topical chemotherapy is given as a creamor ointment applied directly to the cancer, and is common in treatment of certain types of skin cancer. Intravenous (IV) chemotherapy is injected into a vein, and intramuscular (IM) chemotherapy is injected into a muscle. Chemotherapy may also be injected directly into the cancer. This is called intralesional (IL) injection.
Chemotherapy is frequently given through a catheter or port permanently inserted into a central vein or body cavity. A port is a small reservoir or container that is placed in a vein or under the skin in the area where the drug will be given. This eliminates the need for repeated injections and may allow patients to spend less time in the hospital while receiving chemotherapy.
Chemotherapy drugs are toxic to normal cells as well as cancer cells. Many are also designed to attack fast growing cells in the body. Cancer cells grow more quickly than most other body cells. So do cells of the bone marrow (whereblood cells are made), cells in the stomach and intestines, and cells of thehair follicles. Therefore, the most common side effects of chemotherapy arelinked to their effects on these other fast growing cells. Some of these sideeffects include: nausea and vomiting, loss of appetite, hair loss, anemia and fatigue, infection, easy bleeding or bruising, sores in the mouth and throat, damage to the nervous system, and kidney damage.