Radiation oncologists are physicians who are specially trained in the safe use of radiation to treat cancer. Usually, they will manage a patient's entire radiation treatment, from the imaging that will guide decisions, to the choices about what kind of radiation therapy to use.
Radiation is one of the few substances that can kill cancer cells and even shrink tumors. It does this by damaging DNA. When DNA becomes sufficiently damaged, cells can no longer reproduce, and they stop growing and die. Cancer cells are more susceptible to radiation than healthy tissue, because they reproduce faster. So typically, cancer cells exposed to radiation will be affected faster than healthy cells will. However it's still important to protect healthy tissue as much as possible.
There are three ways that radiation can be delivered to the body. It can come from outside the body, delivered by a machine in much the same way x-rays are taken. This is called external-beam radiation. Sometimes the radiation is delivered internally, which is called brachytherapy. Tiny pellets of radioactive material are placed directly onto the cancer, where they can release radiation for a period of time. Some cancers are best treated systemically, with radioactive substances that travel through the bloodstream. Radiation oncologists decide which type of radiation therapy is best, developing a treatment plan for each patient that maximizes the benefits of the radiation while minimizing the risk to any healthy tissue.
Radiation oncologists may work with other kinds of physicians, such as medical oncologists or surgeons, to treat their patients. Sometimes patients are anxious about radiation therapy because it sounds dangerous. But radiation therapy won't turn you radioactive. It's safe, and so effective against many different types of cancer that it is one of the most common cancer treatments. Depending on the treatment, it may not even have noticeable side effects.
Radiation oncologists can be important allies in your fight against cancer.