What Is a Radiation Oncologist?

Medically Reviewed by Dan Brennan, MD on June 24, 2021

More than half of people diagnosed with cancer have radiation therapy, which uses carefully targeted doses of high-energy radiation to kill cancer cells. Radiation oncologists are the highly trained doctors who specialize in this form of care.

What Does a Radiation Oncologist Do?

Radiation oncologists work closely with medical oncologists, surgeons, and other doctors to determine the most appropriate course of treatment for people diagnosed with cancer.

Before performing radiation procedures, radiation oncologists use software to carefully map out where they will deliver radiation to their patients. They also decide which type of radiation therapy to use. The two main types are external beam radiation t herapy and internal radiation therapy.

External Beam Radiation Therapy

External beam radiation therapy comes from a source outside your body that is directed at the cancer site. This is the most common type of radiation therapy, especially for cancers of the head, breast, lung, colon, and prostate.

Internal Radiation Therapy

With internal radiation therapy, your radiation oncologist puts a solid or liquid source of radiation inside your body. With brachytherapy, the radiation source is implanted in or near your cancer. With systemic radiation, the liquid source of radiation is taken through your mouth or a vein. 

Education and Training

The steps to becoming a radiation oncologist include: 

  • Earning a bachelor's degree, particularly in a science-related field
  • Taking and passing the Medical College Admissions Test (MCAT) 
  • Attending medical school and earning your MD or DO degree
  • Completing a residency
  • Fulfilling a fellowship if you wish to specialize in a specific area
  • Obtaining the proper license and certification for the state you’ll be practicing in

Reasons to See a Radiation Oncologist

Radiation oncologists treat many different kinds of cancer. If you’ve been diagnosed with any of the following conditions, you’ll likely need to see a radiation oncologist:

Radiation oncologists also treat conditions other than cancer, including:

What to Expect at the Radiation Oncologist

During your first visit, the radiation oncologist will review your medical records and x-rays, and perform a physical exam. The doctor will talk to you about their findings and decide what treatment plan to choose for you.

You should expect to get radiation treatments five days a week for six to seven weeks. Each visit lasts anywhere from 10 to 30 minutes, but you will only be given radiation for one to two minutes per session. Many small doses are given to help protect the healthy cells in the area being treated, and the two-day break from treatment allows normal cells to recover.

The radiation oncologist will check in with you weekly to see how your body is reacting to treatment.

WebMD Medical Reference



American Cancer Society: “Rising Global Cancer Epidemic.”

American Cancer Society: “How Radiation Therapy Is Used to Treat Cancer.”

David Geffen School of Medicine: “What does a radiation oncologist do?”

Mayo Clinic: “Radiation Oncology.”

National Cancer Institute: “Cancer Statistics.”

National Cancer Institute: “Types of Radiation Therapy.”

Stanford Health Care: “Radiation Therapy: About this Treatment.”

UCHealth: “What Does It Take to Become an Oncologist?”

University of Iowa Health Care: “Radiation therapy - what to expect.”

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