Chemotherapy--or "chemo," as it is commonly called--is the use of medications to treat cancer. Chemo is a systemic therapy that works throughout the entire body. The medications can be administered by injection, intravenously, directly into a body cavity, intrarterially or in pill form. More than 100 chemo drugs are available for cancer therapy. More than one drug at a time is usually used for treatment because the medications work better in combination than by themselves. This practice is termed either "combination chemotherapy" or a "regimen."
Chemotherapy Drugs
Chemotherapy drugs are grouped according to their chemical structure, mechanism of action--or how they relate to another drug. Some drugs act in more than one way and belong in more than one group. Oncologists administer combinations of chemo medications based on how they act, their side effects and how they react with each other. According to the American Cancer Society, here are some of the different groups of chemo drugs commonly used:
• Alkylating agents--prevent cancer cells from reproducing by directly damaging their DNA.
• Antimetabolites--stop the growth of cancer cells by blocking necessary enzyme pathways.
• Anthracyclines--anti-tumor antibiotics that disturb enzymes in order to stop DNA replication in cancer cells.
• Topoisomerase inhibitors--inhibit specific enzymes called topoisomerases used in the process of DNA replication of cancer cells.
• Corticosteroids--natural hormones or hormone-like drugs that are used to kill and slow the growth of cancer cells.
• Mitotic inhibitors--substances derived from plants and natural sources that are used to stop mitosis (one cell dividing into two) of cancer cells and inhibit enzymes needed for cell reproduction.
Chemotherapy Regimens
Drugs that have different actions can be combined in order to kill more cancer cells and prevent resistance by the cancer to any one chemo medication. Hundreds of regimens are commonly used by doctors based on the fact that certain combinations of drugs are more effective with certain types of cancers. Regimens are often named based on the first letter of the names of the drugs that are combined. The following list describes regimens for common types of cancers:
• Breast cancer--regimen AC (doxorubicin, cyclophosphamide), and Regimen CMF (cyclophosphamide, methotrexate, 5-fluorouracil).
• Colon cancer--regimen CapeIRI (capecitabine, irinotecan).
• Leukemia--regimen AIDA (all-trans retinoic acid, idarubicin)
• Melanoma--regimen CVD (cisplatin, vinblastine, dacarbazine)
• Lung cancer--regimen CAE (cyclophosphamide, doxorubicin, etoposide)
Side Effects
Although not everyone gets sick from chemo, chemotherapy drugs are potent and many cause side effects. They kill cancerous cells as well as some normal and healthy cells within your body. Cells that grow quickly are the ones that are mostly harmed by chemo, and side effect symptoms will vary depending on the type of cells affected. Damage to bone marrow cells can make you feel tired, bleed easily and have a weakened immune system. Hair loss can occur when hair growth cells are affected by chemo. Dry skin, sores and dry mouth are symptoms of injury to skin and mouth cells. When chemotherapy affects the cells in your stomach and intestines, you can experience nausea, vomiting and diarrhea. If side effects are extreme, your doctor may need to adjust the dosages and cycles of your chemotherapy. Most unwanted effects are short-term and cease after treatment.
