Colon cancer is a type of cancer that develops in the tissues of the colon, which is the longest part of the large intestine and comprises the lower part of the digestive system. Radiation therapy is used to treat colon cancer painlessly and noninvasively. External beam radiation therapy (EBRT) is an effective treatment for colon cancer, working within cancer cells to damage their ability to multiply. During treatment, high-energy X-rays are delivered to the cancer with a linear accelerator (LINAC). Treatments are delivered daily Monday through Friday. Each treatment takes about 10 to 15 minutes. The treatment process is painless, safe and will not burn or hurt you. Side effects are usually minimal, and most patients return to routine activities immediately after each treatment. Several factors determine candidacy for radiation therapy treatment including the stage of the cancer, potential side effects, age and overall health. Sometimes a combination of treatments is the best plan for treating colon cancer.