For many years, the
treatment of cancer was focused primarily on surgery, chemotherapy, and radiation. However, as researchers
learn more about how the body fights cancer on its own, therapies are being developed that harness the potential of the body''s defense system in this fight, including efforts to prevent some forms of cancer. Therapies that use the immune system to fight or prevent cancer are called biological therapies.
The FDA has, however, approved two vaccines that can help prevent cancer. One of these vaccines prevents infection with the human papillomavirus (HPV), which causes almost all cervical cancers (for more information, see Human Papillomavirus (HPV) Vaccines for Cervical Cancer). The other vaccine prevents infection with the hepatitis B virus, which can cause liver cancer. Other vaccines that may prevent or reduce the risk of cancer are also being tested in ongoing clinical trials.
Cancer
treatment vaccines can be made using a patient’s own tumor
antigens or cells, or someone else’s. Most tumors of a given type share many antigens. When a patient’s own tumor antigens or cells are used, the vaccine is called an autologous vaccine. When someone else’s tumor antigens or cells are used, the vaccine is called an allogeneic vaccine.
Cancer vaccines often have added ingredients, called adjuvants, that help boost the immune response. These substances may also be given separately to increase a vaccine’s effectiveness. Many different kinds of substances have been used as adjuvants, including cytokines, proteins, bacteria, viruses, and certain chemicals.
Cancer vaccines are intended either to treat existing cancer or to prevent the development of cancer. Cancer treatment vaccines are designed to strengthen the body''s natural defenses against a cancer that has already developed. These vaccines may stop an existing tumor from growing, stop a tumor from coming back after it has been treated, or eliminate cancer cells not killed by previous treatments.
Cancer preventive vaccines are given to healthy people and are designed to target infectious agents that can cause cancer. The HPV vaccine is an example of a cancer preventive vaccine. It is used to help prevent cervical cancer.
Much work also remains to be done to develop vaccines that can reliably prevent cancers associated with infectious agents. Cervical cancer, for example, is almost always caused by infection with HPV. The FDA has approved a vaccine that prevents infections with two types of HPV that cause nearly 70 percent of all cervical cancers. Researchers must develop new vaccines that are able to prevent infections by all HPV types that can cause this disease.
Ongoing trials seek to find the most promising situations for the use of cancer vaccines and the best approaches for making such vaccines work. Only when rigorous trials provide evidence that a particular cancer vaccine is both safe and effective against a specific type of cancer will the FDA consider approving that vaccine as standard treatment.