American Medical Association Family Medical Guide - American Medical Association [21]
Radiation therapy
Radiation therapy uses penetrating beams of high-energy radioactive waves or streams of radioactive particles to treat cancer. This radioactive energy, which is the same as that used in X-rays but in much higher doses, kills the cancer cells or keeps them from dividing. Healthy cells are also affected by radiation but, unlike cancer cells, healthy cells tend to recover from the effects of radiation.
More than half of all people with cancer are treated with some form of radiation. Radiation is often used before surgery to shrink a tumor or after surgery to block the growth of any cancer cells that could remain in the area around the tumor. Radiation therapy is also often combined with chemotherapy (see below).
Radiation therapy can be given either externally or internally. Most people receive the external form, in which a machine directs the high-energy rays at the tumor and a small margin of surrounding tissue. In internal radiation therapy, the radiation is provided by a source placed inside the body, such as an implant, an injection, or a medication.
Side effects from radiation therapy vary from person to person and depend on the dose of radiation and the area of the body being treated. The most common side effects—including fatigue, skin changes, and loss of appetite—usually clear up within a few weeks.
Stereotactic radiation therapy
Some newer radiation techniques are almost as precise as surgery. By aiming radiation at a cancer target from different angles, stereotactic radiation therapy can deliver a large, precise dose of radiation to a small tumor. The procedure is so precise that it is often called stereotactic surgery and the machine that delivers the energy waves is called a gamma knife (even though no incision is actually made). Stereotactic radiation therapy has been used mostly to treat tumors in the brain but is being investigated as a way to treat other types of cancer.
External radiation therapy
The most common type of machine used for external radiation therapy is the linear accelerator, which fires high-energy rays at a tumor to shrink it. In this photograph, the tumor is in the person’s head, which is stabilized by a steel frame.
Chemotherapy
Chemotherapy is the treatment of cancer with powerful drugs that can destroy cancer cells by preventing them from dividing. Two or more drugs are often given at the same time because they are more effective when combined.
Most people receive chemotherapy on an outpatient basis, usually at home, in a doctor’s office, or at a clinic. The drugs can be administered intravenously (through a vein), by mouth, in an injection, or in a skin patch.
During chemotherapy, healthy, normal cells that divide quickly (such as those in hair follicles) can be harmed by the drugs. This damage to healthy cells is the cause of most of the side effects of chemotherapy, including hair loss, fatigue, nausea and vomiting, diarrhea, constipation, pain, anemia, and confusion.
Doctors also treat cancer with drugs that work in other ways. For example, biological therapy uses substances that strengthen the body’s immune system to fight the cancer. Other drugs block the effects of specific hormones or other body chemicals that can promote particular types of cancer.
Genetics
Genes play a role in all diseases, including the common cold. Researchers have discovered many of the genes that cause inherited disorders, and they are beginning to find the genes that interact with environmental factors (such as lifestyle) to cause common health problems such as heart disease, cancer, and diabetes. Advances in genetics research will enable us to take steps to modify our habits to avoid many of these disorders. This new knowledge will also spark the development of more effective, more targeted treatments that have fewer adverse effects. The more you know about your genetic