Radiation oncology is a local, regional treatment that uses high energy x-rays to damage cancer cells and prevent them from growing. Radiation treatments only affect cells in the treated area. External radiation is usually given on an outpatient basis, 5 days per week, for a total of 20-45 treatments, depending on what is prescribed by the physician. Patients are not radioactive during or after their treatment. Side effects depend on the area being treated and will be discussed prior to treatment initiation. The side effects are usually mild and can be treated or controlled.