Radiation therapy uses high-energy particles or waves, such as x-rays, gamma rays, electron beams, or protons, to destroy or damage cancer cells. Your cells normally grow and divide to form new cells. But cancer cells grow and divide faster than most normal cells. Radiation works by making small breaks in the DNA inside cells. These breaks keep cancer cells from growing and dividing and cause them to die. Nearby normal cells can also be affected by radiation, but most recover and go back to working the way they should. While chemotherapy and other treatments that are taken by mouth or injection usually expose the whole body to cancer-fighting drugs, radiation therapy is usually a local treatment. This means it’s usually aimed at and affects only the part of the body needing treatment. Radiation treatments are planned so that they damage cancer cells with as little harm as possible to nearby healthy cells. Some radiation treatments (systemic radiation therapy) use radioactive substances that are given in a vein or by mouth. Even though this type of radiation does travel throughout the body, the radioactive substance mostly collects in the area of the tumor, so there’s still little effect on the rest of the body. People who needradiation therapy? More than half of people with cancer get radiation therapy. Sometimes, radiation therapy is the only cancer treatment needed and sometimes it's used with other types of treatment. The decision to use radiation therapy depends on the type and stage of cancer, and other health problems a patient might have. Objective of radiation therapy? Most types of radiation therapy don’t reach all parts of the body, which means they’re not helpful in treating cancer that has spread to many places within the body. Still, radiation therapy can be used to treat many types of cancer either alone or in combination with other treatments. While it's important to remember each cancer and each person is different, radiation is often the treatment of choice for the following purposes. Cure early-stage cancer Some cancers are very sensitive to radiation. Radiation may be used by itself in these cases to make the cancer shrink or completely go away. In some cases, chemotherapy or other anti-cancer drugs may be given first. For other cancers, radiation may be used before surgery to shrink the tumor (this is called preoperative therapy or neoadjuvant therapy), or after surgery to help keep the cancer from coming back (called adjuvant therapy). For certain cancers that can be cured either by radiation or by surgery, radiation may be the preferred treatment. This is because radiation can cause less damage and the part of the body involved may be more likely to work the way it should after treatment. For some types of cancer, radiation and chemotherapy or other types of anticancer drugs might be used together. Certain drugs (called radiosensitizers) help radiation work better by making cancer cells more sensitive to radiation. Research has shown that when anti-cancer drugs and radiation are given together for certain types of cancer, they can help each other work even better than if they were given alone. One drawback, though, is that side effects are often worse when they are given together. Recurring of Cancer Cancer can spread from where it started to other body parts. Doctors often assume that a few cancer cells might already have spread even when they can’t be seen on imaging scans like CT scans or MRIs. In some cases, the area where the cancer most often spreads to may be treated with radiation to kill any cancer cells before they grow into tumors. For instance, people with certain kinds of lung cancer may get radiation to the head, even when there is no cancer known to be there, because their type of lung cancer often spreads to the brain. This is done to help prevent cancer from spreading to the head even before it can. Sometimes, radiation to prevent future cancer can be given at the same time that radiation is given to treat existing cancer, especially if the area the cancer might spread to is close to the tumor itself. Treatment of symptoms caused by advanced cancer Sometimes cancer has spread too much to be cured. But some of these tumors can still be treated to make them smaller so that the person can feel better. Radiation might help relieve problems like pain, trouble swallowing or breathing, or bowel blockages that can be caused by advanced cancer. This is called palliative radiation. Treatment of recurred Cancer If a person's cancer has returned (recurred), radiation might be used to treat the cancer or to treat symptoms caused by advanced cancer. Whether radiation will be used after recurrence depends on many factors. For instance, if the cancer has come back in a part of the body that has already been treated with radiation, it might not be possible to give more radiation in the same place. It depends on the amount of radiation that was used before. In other instances, radiation might be used in the same area of the body or a different area. Some tumors do not respond as well to radiation, so radiation might not be used even if they recur. Radiation therapy Methodologies ? Radiation therapy can be given in 3 ways: External radiation (or external beam radiation): uses a machine that directs high-energy rays from outside the body into the tumor. It’s done during outpatient visits to a hospital or treatment center. It's usually given over many weeks and sometimes will be given twice a day for several weeks. A person receiving external radiation is not radioactive and does not have to follow special safety precautions at home. Internal radiation: Internal radiation is also called brachytherapy. A radioactive source is put inside the body into or near the tumor. With some types of brachytherapy, radiation might be placed and left in the body to work. Sometimes it is placed in the body for a period of time and then removed. This is decided based on the type of cancer. Special safety precautions are needed for this type of radiation for a period of time. But it's important to know if the internal radiation is left in the body, after a while it eventually is no longer radioactive. Systemic radiation: Radioactive drugs given by mouth or put into a vein are used to treat certain types of cancer. These drugs then travel throughout the body. You might have to follow special precautions at home for a period of time after these drugs are given. The type of radiation you might get depends on the kind of cancer you have and where it is. In some cases, more than one type is used. Your cancer care team can answer specific questions about the type of radiation prescribed for you, how it affects your body, and any precautions that may be needed.