Immunotherapy Biological therapy (also called immunotherapy, biological response modifier therapy, or biotherapy) uses the body's immune system to fight cancer. The cells, antibodies, and organs of the immune system work to protect and defend the body against foreign invaders, such as bacteria or viruses. Doctors and researchers have found that the immune system might also be able to both determine the difference between healthy cells and cancer cells in the body, and to eliminate the cancer cells. (By itself, the immune system is not always good at destroying cancer cells; if it were, people would not get cancer.) Biological therapies are designed to boost the immune system, either directly or indirectly, by assisting in the following: Stop, control, or suppress the processes that allow cancers to grow Making cancer cells more recognizable by the immune system, and therefore more susceptible to destruction by the immune system Boosting the killing power of immune system cells Changing the way cancer cells grow, so that they act more like healthy cells Stopping the process that changes a normal cell into a cancerous cell Enhancing the body's ability to repair or replace normal cells damaged or destroyed by other forms of cancer treatment, such as chemotherapy or radiation Preventing cancer cells from spreading to other parts of the body Biological therapies can be used alone to treat cancer or can be combined with other treatments such as chemotherapy and radiation therapy. To learn more about immunotherapy, click here.