Immunotherapy
The purpose of immunotherapy is to stimulate the body's immune system against cancer. Some forms of immunotherapy use vaccines composed of antigens derived from tumor cells to boost the body's production of antibodies or immune cells (T lymphocytes). Substances such as extracts of weakened tuberculosis bacteria, which are known to boost the immune response, have been successful when applied locally to bladder cancers. To date, other vaccines have not proven useful in the treatment of cancer.
Monoclonal antibody therapy involves the use of experimentally produced antibodies to specific proteins on the cell surface. Trastuzumab is one such antibody. It helps women with advanced breast cancer when given alone or in combination with a variety of chemotherapy drugs. Rituximab may be helpful for lymphomas and chronic lymphocytic leukemia. Gemtuzumab ozogamicin, a combined antibody and drug, is effective in some people with acute myelocytic leukemia. Antibodies linked to a radioactive isotope can be used to deliver radiation directly to the cancer cells.
Biologic response modifiers are used to improve the immune system's ability to find and destroy cancer cells, such as by stimulating normal cells to produce chemical messengers (mediators). Interferon (of which there are several types) is the best-known and most widely used biologic response modifier. Almost all human cells produce interferon naturally, but it can also be made artificially using recombinant technology. Although its precise mechanisms of action are not totally clear, interferon has a role in the treatment of several cancers. Measurable responses have occurred in about 30% of people with Kaposi's sarcoma, the majority of people with chronic myelocytic leukemia, and in 10 to 15% of people with renal cell carcinoma and malignant melanoma.
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