This page was reviewed under our medical and editorial policy by
Kevin King, MD, Radiation Oncologist, City of Hope | Downtown Chicago
This page was updated on December 22, 2023.
About 5,338 radiation oncologists are practicing in the United States today, according to 2017 data from the U.S. Department of Health and Human Services (HHS). With a population of more than 321 million, that means a ratio of fewer than two radiation oncologists per 100,000 people. Most are found in metropolitan areas. However, radiation oncologists also may practice in smaller communities with academic medical centers. The number of facilities that provide radiation therapy has grown by about 17 percent over the past 15 years, according to data presented at the 2020 American Society for Radiation Oncology Annual Meeting. The distance most patients have to travel for treatment has improved slightly, with nearly 70 percent of the U.S. population within 12.5 miles of a radiation facility (up from 65.4 percent in 2005). Yet still, 4.5 percent of Americans are farther than 50 miles away from radiation care.
Radiation therapy (also called radiotherapy) is used to treat a number of cancers. The treatment typically uses X-rays to kill cancer cells and shrink tumors. About 60 percent of all cancer patients receive radiation therapy at some time during their illness, according to the National Cancer Institute. Radiation therapy may be used as palliative care.
Physicians who oversee the care of cancer patients undergoing radiation treatment are known as radiation oncologists. They determine whether patients are candidates for radiation therapy and outline the benefits and side effects of radiation treatment. Radiation oncologists also make sure the amount of radiation given is appropriate and monitor the patient’s progress during treatment. There are different types of radiation therapy, and radiation oncologists recommend certain strategies based on the cancer type and stage of cancer.
Radiation oncologists work closely with other doctors on the cancer treatment team. A medical oncologist may be on the team if chemotherapy is part of the treatment plan. A medical oncologist specializes in administering chemotherapy and other targeted agents used to kill the cancer or slow down its growth. A surgical oncologist also may be part of the team if the treatment plan includes removing tumors or performing biopsies to help diagnose cancer.
Radiation oncologists have completed four years of college and four years of medical school, including one year of general medical internship. After choosing radiation oncology as their specialty, they also complete a four-year residency in that area. They are trained in the use of radiation to safely treat disease. Radiation oncologists are certified by the American Board of Radiology after passing its exam. They must stay up-to-date in their field to maintain certification. Before receiving treatment, patients should ask if their radiation oncologist is board certified.
All cells grow, divide and multiply, but cancer cells go through this cycle faster than normal, healthy cells. Cancer treatments, including radiation therapy, are designed to damage the cancer cells’ DNA so they stop growing or die.
Radiation therapy is different from other cancer treatments, such as chemotherapy, because it is localized. The radiation is aimed at the part of the body where the cancer is located. With most radiation techniques, the radiation does not go through the entire body and patients will not become radioactive. Radiation oncologists try to limit harm to healthy tissue as much as possible when they use radiation.
Radiation therapy is used to treat many cancers. It’s also used to treat cancer that has recurred or spread to other parts of the body. Some cancers may be treated with radiation therapy alone, while others require a combination of treatments that may include radiation therapy.
Like other cancer treatments, radiation therapy may cause some side effects. Although it may destroy an existing cancer, radiation therapy may also increase the risk of developing another cancer in the future. There’s also a limit to the amount of radiation any one area of the body may receive in a lifetime, but another area of the body may still be treated with radiation therapy if it’s far enough from the original treatment site.
Types of radiation therapy include:
External-beam radiation: This is the most commonly used type of radiation therapy. A machine called a linear accelerator is used to deliver radiation from outside the body. Specialized computer software is used to adjust the size and shape of the beam needed to target the cancer. Types of external-beam radiation include:
Internal radiation therapy: Also called brachytherapy, internal radiation therapy places radioactive material inside or nearby the cancer. The placement may be temporary or permanent. There are different types of internal radiation therapy, including:
Intraoperative radiation therapy (IORT): During surgery, the surgeon moves healthy tissue out of the way so either external beam or internal beam radiation therapy may be used. IORT may be used when vital organs are close to the tumor.
Systemic radiation therapy: Radioactive material is given orally or by injection. The material is flushed from the body through saliva, urine and sweat. This type of radiation therapy may be used to treat thyroid cancer with radioactive iodine.
Molecular radiotherapy or targeted radionuclide therapy: This type of systemic radiation therapy is used to treat some patients with advanced prostate cancer or gastroenteropancreatic neuroendocrine tumor.
Familiarity with the treatment and side effects may help make receiving radiation therapy less stressful. Here are some questions to ask providers about radiation therapy: