Radiation therapy is the careful use of high-energy radiation (such as x-rays or electrons) to treat cancer. Radiation therapy works by destroying the cancer cells' ability to reproduce. The body then naturally gets rid of these cells.
Radiation may be used to cure cancer; prevent local regrowth of the cancer; or relieve symptoms, such as pain. It is commonly combined with chemotherapy or surgery, depending on the type and location of the cancer.
A radiation oncologist may use radiation generated by a machine outside a patient's body (external radiation therapy) or radioactive sources that are placed inside the patient (brachytherapy).
Radiation is targeted at the tumor using a machine called a linear accelerator, or linac. With careful treatment planning, the surrounding normal tissue can be spared.
The treatment process can take 10 to 30 minutes each day with most of the time spent positioning the patient. Patients usually receive radiation treatments once a day, five days a week, for a total of two to nine weeks. Occasionally, treatments are given twice a day. The total duration of a course of radiation depends on the patient’s diagnosis and overall health and the goal of treatment.
Intensity-modulated radiation therapy (IMRT) is an advanced method of external beam treatment that results in the radiation dose more closely matching the three-dimensional shape of the tumor. With IMRT, the radiation oncologist can deliver higher radiation doses to tumors with fewer side effects compared with conventional external beam techniques. Currently, IMRT is being used most extensively to treat cancers of the prostate, head and neck, breast, and central nervous system.