If a malignant tumor (cancer) goes untreated, then it can spread to other areas of the body, form other tumors and ultimately kill a person. According to the American Cancer Society, "Radiation therapy uses high-energy particles or waves to destroy or damage cancer cells. It is one of the most common treatments for cancer, either by itself or along with other forms of treatment."
Radiation treatment of today uses very sophisticated equipment which targets only the general area of the body. While it will also kill some of the surrounding healthy cells around the tumor, those cells can repair themselves, while the malignant cells get entirely destroyed.
The treatment itself is entirely painfree and does not take more than a few minutes per day. Traditionally, treatments are given 5 days a week, for 1 to 10 weeks, with a break on the weekends.
Before the treatment starts, patients are usually measured in various ways so that the doctors can formulate a plan, calculate the exact amount of radiation and also, sometimes, to make a mold around the body, so that the person can remain still and in the in the exact same position every time.
The worst part of radiation treatment is not the treatment itself, but the side effects, which can include extreme fatigue after a few weeks, achey or sore areas of the body (depending on where the radiation is being given) and also, most commonly, burnt skin -- as if the person has a very bad sun burn. Because the treatment is accumulative, the burns on the skin can sometimes open up, and if that happens, the therapy may have to be paused for a few days to allow the skin to heal. During the actual treatment, the person visits a clinic or hospital every day and lays on a flat table, under the radiation machine. The radiation therapist will adjust the person's body inside a mold and sometimes place special shields to protect the other organs.