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| Cancer cells that are fast-growing are most susceptible to chemotherapy, which kills them by various mechanisms that usually act at different stages of the mitotic (cell-division) cycle. The potent chemicals that chemotherapy uses to kill cancer cells are given by mouth or injected into a vein or muscle, beneath the skin, into an artery, into the spinal cord, or into the lung or abdominal cavities. |
| Alkaloids, which are natural compounds derived from plants, such as the periwinkle, are made into chemotherapeutic agents. Alkylating agents work differently, in that they bind nonspecifically to DNA and protein to inhibit cell growth. Some antibiotics from molds, such as actinomycin-D, are also used as chemotherapeutic drugs. |
| General guidelines for administering cancer chemotherapy recommend that the highest tolerated dose be used and that several drugs be used in combination. The use of high doses, the systemic administration, and the toxic properties of many anticancer drugs account for the often severe side effects of chemotherapy. Some cancers are resistant or become resistant to the effects of some of the drugs. The emergence of resistant clones and the regrowth of drug-resistant cancers is a particular problem during and after treatment. |
| Efforts to improve the effectiveness of chemotherapy include: |
| 1. Developing ways to specifically target the tumor. |
| 2. Linking cell-killing agents to monoclonal antibodies that are attracted to specific proteins on the surface of the cancer cells. |
| 3. Further developing photodynamic therapy (PDT), which beams light into a tumor that has been injected with hematoporphyrin, a chemical that causes oxygen to become toxic to the cells it touches. The use of this localized cancer treatment is still quite limited. PDT capitalizes on the greater attraction of hematoporphyrin molecules to rumor tissue rather than to normal tissue. |
| Major Types of Chemotherapy |
| Alkylating Agents |
| These agents block reproduction of the chain of cancer cell DNA during cell division. |
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