Chemotherapy
Chemotherapy involves the use of drugs to destroy cancer cells. Although an ideal chemotherapy drug would destroy cancer cells without harming normal cells, few such drugs exist. Instead, in chemotherapy, drugs are designed to inflict greater damage on cancer cells than on normal cells. Nonetheless, all chemotherapy drugs affect normal cells and cause side effects.
Not all cancers respond to chemotherapy. The type of cancer determines which drugs are used, in what combination, and at what dose. Chemotherapy may be used as the sole treatment or combined with radiation therapy and surgery.
One approach is to use a variety of "molecularly targeted" drugs that can enter cancerous (malignant) cells and interrupt important pathways of information flow in the cell. These molecules render the cells defective, and they die. Imatinib, the first such drug, alters the energy site in the malignant cell and is highly effective in chronic myelocytic leukemia and certain tumors of the digestive tract. Other such drugs target cell surface receptors in nonsmall cell lung cancer and colon cancer, but are not yet available for general use.
Dose-intensity chemotherapy is a new but risky approach in which especially high doses of drugs are used. This therapy is used for a few types of cancer (including some types of myeloma, lymphoma, and leukemia) that have recurred even though the person had a good response when first treated with drugs. Because such tumors have already demonstrated sensitivity to the drug, the strategy is to markedly increase the drug dose to kill more cancer cells and thus prolong the person's survival.
However, dose-intensity chemotherapy can cause life-threatening injury to the bone marrow. Therefore, dose-intensity chemotherapy is commonly combined with bone marrow rescue strategies, in which marrow cells are harvested before the chemotherapy is administered and returned to the person after chemotherapy. In some cases, stem cells can be isolated from a blood sample and used instead of bone marrow to restore the bone marrow.
 See the drug table Chemotherapy Drugs.
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