While surgery and radiation treat cancers that are growing in one particular place, chemotherapy is generally used for cancers that have traveled through the blood and lymph systems to many parts of the body. In the past, chemotherapy was used only when surgery and radiation were no longer effective. But now it is the treatment of choice for some kinds of cancer and is often used in combination with surgery and radiation, especially for localized cancers.
Biological Therapy This is a relatively new way to treat cancer. It takes advantage of recent
research that shows that the immune system may play a key role in protecting the body against cancer. The immune system might even play a part in combating cancer that has already developed.
The immune system consists of white blood cells called lymphocytes that act as a defense system against foreign organisms such as bacteria and viruses. One type of lymphocyte—the T cell—is formed in the thymus gland and is a natural killer of foreign cells, including cancer cells. Another lymphocyte—the B cell—is produced in the bone marrow and lymph nodes and makes antibodies in response to stimulation by a foreign protein. B lymphocytes can also kill cancer cells. Another white cell—the monocyte—interacts with T and B cells.
Biological therapy consists mainly of using highly purified proteins—interferon and interleukin-2 are the best known—to activate the immune system. In many different ways, they boost the lymphocytes' cancer-killing properties.
