Radiation Therapy

How is radiation therapy used?

Doctors can use radiation therapy in a number of ways to treat cancer.

  • Early stage cancer: radiation sometimes is the only treatment needed to shrink tumors or cause cancer cells to disappear
  • Before surgery: radiation is sometimes used before surgery to shrink a tumor so it can more easily be removed.
  • After surgery: radiation may be recommended after surgery to keep any cancer cells that remain from growing.
  • With chemotherapy: radiation may be used in combination with chemotherapy to kill cancer cells.

How exactly does radiation therapy work?

All cells, healthy or not, grow and divide. Cancer cells grow and divide faster. Radiation changes the DNA inside a cancer cell so that it cannot grow. Radiation therapy targets only the tumor or location of the cancer and the area that surrounds it.

What types of cancer can be treated with radiation?

Early stage cancer and cancer known to spread to other specific areas of the body can benefit from radiation therapy. It can also be used to help kill remaining cancer cells that could still be hidden or undetected in your body. In some cancers, radiation therapy is recommended because it can help to relieve symptoms such as swallowing or breathing difficulty due to the location of a tumor.

What types of cancer radiation are used?

Doctors have several forms of radiation that can be used to kill cancer cells, depending upon where cancer cells are located. The radiation can come from outside of your body or be implanted.

External Beam Radiation Therapy

These radiation beams start outside of the body and are directed into the body to where the cancer cells are located. Higher doses of radiation typically can go deeper into the body’s tissues to reach the cancer. Doctors may use one or multiple radiation beams to treat cancer and can vary the amount of radiation from each beam. Beams also can be positioned to enter from almost any angle and be shaped to match the characteristics of a tumor.  External radiation can come in the form of x-rays, gamma rays, or proton beams, among others.

Internal Radiation Implants

Some types of cancer are treated with small “seeds” or implants of radioactive materials directly into or next to a tumor. This procedure is called brachytherapy. Implants can either remain in the body or be removed once depleted.

How much radiation will I receive?

Your doctor will prescribe the exact type of radiation and dose needed. All patients receiving radiation therapy will be scheduled for pre-treatment planning sessions so that the location and size of your cancer or tumor can be mapped precisely.

Patients receiving radiation typically are scheduled for daily treatments (usually five days a week for a set period). The number of days depends upon the type and stage of cancer and where it is located as well as whether the radiation is combined with other treatments, such as surgery or chemotherapy. Typically, the length of time for radiation treatments ranges from two to eight weeks.

Radiation Oncology History of Excellence

Radiation Oncology services have a long and rich history at Washington University, dating back to 1951 when the Mallinckrodt Institute of Radiology (MIR) first established a radiation therapy section, a relatively new concept in the medical community at the time. After many years of growth within MIR, the Department of Radiation Oncology was formally established in 2001, and has continued to be a leader in patient care and technological innovation.

The department is one of the largest in the United States, and a national leader in developing the most recent radiation treatments for cancer patients. We offer the widest range of radiation therapy options in the Midwest, allowing our physicians to tailor treatment to each individual patient’s needs. We are a national leader in radiation oncology clinical trials and rank as the highest academic accrual site for cooperative group therapeutic trials. The department’s clinical programs consist of several centers of excellence including Brachytherapy, Stereotactic Radiosurgery and the Proton Therapy Center.

Each of our radiation oncologists are clinically specialized, focusing exclusively on two to three different types of cancer in order to best serve our patients. This focus on a few of the various types of cancer allows our physicians to develop unparalleled expertise.

In 2017, the department received accreditation through the American Society of Radiation Oncology Accreditation Program for Excellence (APEx), highlighting the department’s ongoing commitment to providing safe, high-quality radiation therapy services to its patients.

The department is a leader in introducing innovative technologies. It was the first Department of Radiation Oncology in St. Louis and the Midwest to offer proton therapy, ultrasound-guided permanent seed prostate implants, high dose rate brachytherapy for a variety of anatomical sites, stereotactic radiosurgery, intensity modulated radiotherapy (IMRT), three-dimensional treatment planning, MRI-guided radiotherapy, and clinical trials with radioimmunotherapy.


Early developments: Washington University was instrumental in the development of many different technologies and techniques to improve patient care, such as CT scanning, positron-emission tomography (PET), and 3-dimensional treatment planning. Department faculty collaborated with industry to develop the Clinac 35 Accelerator, a first generation of linear accelerators featuring built-in computers and the capability to produce short-lived radioactive isotopes. William Powers, MD, the first director of Radiation Therapy, developed a process in which custom-built blocks made of cerrobend alloy could be used to block the delivery of radiation to areas outside of the treatment site.

Biological advances: Cancer Biology scientists in the Department of Radiation Oncology developed a technique for simplifying the identification of hormone-responsive tumors and improving the reliability of assay procedures. Current research focuses in the division include drug development, bioinformatics/omics, imaging, and preclinical modeling.

Gamma Knife: In clinical use at Washington University since 1998, the Gamma Knife stereotactic radiosurgery service represents a multi-disciplinary collaboration between radiation oncology and neurosurgery. Many patients only receive a single treatment using this technique, which uses a pinpoint beam of radiation to treat cancerous tissue in the brain. Gamma Knife can also be used to treat some functional neurologic disorders such as epilepsy, trigeminal neuralgia, and essential tremor.

Proton Therapy: The first patient treatment on the world’s first compact proton therapy system was conducted at the S. Lee Kling Center for Proton Therapy at Siteman Center in December 2013. Proton therapy allows for better control over the shape and depth of the radiation treatment beam, which can be advantageous when treating tumors near critical organs, such as the heart or brain. This level of control can often be beneficial for pediatric patients as it can often spare patients from receiving excess radiation to normal tissues. Due to the department’s early adoption of proton therapy, staff at the S. Lee Kling Center for Proton Therapy have been highly involved in the development of treatment planning and quality assurance processes for users of this machine all over the world.

MRI-guided radiotherapy: In January 2014, the world’s first magnetic resonance image (MRI) guided radiation therapy treatment was performed at Washington University School of Medicine. This technology allows the treatment team to observe tumor movement during treatment, and deliver radiation only when the treatment site is in precisely the right position. Patients whose treatment sites might be affected by things like motion from breathing can often benefit from treatment with MRI-guided radiotherapy. In addition to being the first clinical site to use this technique to its full clinical capacity, the ViewRay MRIdian system used to deliver this type of treatment was developed by a graduate of the department’s medical physics residency program.

Commitment to Education: The Department of Radiation Oncology at Washington University established a training program for radiation therapy technologists in 1966. The program, initiated by former chairman Carlos A. Perez, MD, was the first of its kind in the United States, and became nationally recognized for its standard of excellence. The Department of Radiation Oncology’s medical physics residency program, established in 1992, was the first program of its kind to be accredited by the Commission on Accreditation of Medical Physics Education Programs (CAMPEP).

Washington University Department of Radiation Oncology

To learn more about the Department of Radiation Oncology at Washington University School of Medicine, please visit their website http://radonc.wustl.edu/.