Types of Radiation Therapy

Along with surgery and infusion therapy, radiation therapy is one of the three pillars of cancer treatment. Currently, nearly two-thirds of individuals diagnosed with cancer will receive some form of radiation therapy.

Depending on your cancer, you may have one of the following types of radiation therapy.

External Beam Therapy

External beam therapy is the most common type of radiation treatment and what most people imagine when they think of radiation therapy. As the name suggests, the radiation is generated externally and delivered to the tumor in highly focused beams (photons).

UC San Diego Health uses Varian Medical Systems linear accelerators for our external beam treatments. Our Varian systems are at the forefront of cancer care, fully integrated with other sophisticated technologies that allow our care teams to safely implement high-precision treatments, not widely available elsewhere. In 2017, for example, we were one of only two healthcare systems in the world to offer Varian's Halcyon system. Its newest linear accelerator simplifies and enhances the delivery of therapeutic radiation improving patient comfort during treatment.

Many approaches for delivering external beam radiation exist, and we use multiple add-on technologies to improve the targeting of cancerous cells. These add-on technologies include:

  • AlignRT, a camera tracking and imaging system that helps manage any movement of the patient that would alter the optimum positioning of the beams
  • CT-guided imaging (also known as conformal radiation therapy), which allows us to simulate and map your treatment plan using high-resolution scans of the tumor site. 
  • Image-guided radiation therapy, an imaging system that adjusts the position of the radiation beams to take into account changes in the position of a tumor and/or patient between and during treatments. In simple terms, the technology helps ensure that your treatments are precisely delivered on a daily basis.
  • Intensity-modulated radiation therapy (IMRT), a type of conformal radiation therapy that allows for the intensity of radiation to be modified during treatment to better preserve healthy adjoining tissue. Most of our patients will receive IMRT. UC San Diego Health has been a pioneer in the development of IMRT as a treatment for gynecologic cancers.

Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) is a type of external beam therapy that delivers high doses of radiation to a tumor more precisely than a scalpel can cut away cancerous tissue. It is used to treat tumors of the brain. 

Stereotactic Body Radiotherapy

When stereotactic radiosurgery is used to treat tumors in the body, it is called stereotactic body radiotherapy (SBRT). UC San Diego Health physicians use SBRT to treat cancerous cells scattered in the neck, spine and lung, particularly in areas near the heart.

Total Body Irradiation

Total Body Irradiation (TBI) is a type of external beam therapy that involves irradiation of the entire body, in conjunction with chemotherapy in individuals undergoing stem cell transplantation for blood cancer or a blood disorder. The purpose of TBI is to eradicate remaining cancer cells and suppress the immune system to help reduce the risk of tissue rejection. Though the entire body is irradiated, we take great care to protect normal lung tissue by placing customized metal alloy lung blocks over the lungs during treatment.

Proton Therapy

Proton therapy is a type of radiosurgery that uses protons (heavy, charged particles) instead of photons (x-rays) to target cancer cells. It is best suited for localized solid tumors near sensitive healthy tissue and has been shown to have similar cure rates to external beam therapy but with fewer side effects and diminished long-term toxicity in some cancers. Because of these potential benefits, proton therapy may be a preferred treatment approach for certain adult and pediatric cancers. Patients with UC San Diego Health have access to proton therapy through our affiliation with California Protons Cancer Therapy Center, the only proton therapy center in the region.


Brachytherapy uses radioactive material that is either implanted inside the body at the tumor site or placed near the tumor site for a few minutes. 

UC San Diego Health offers:

  • Low-dose rate (LDR) brachytherapy, which may be used to treat prostate cancer. The approach protects sensitive surrounding tissue from damage by inserting tiny permanent radioactive seeds into the prostate. (We offer other radiation therapy options for prostate cancer, too.) LDR techniques are also used to treat cancers of the eye while sparing vision. Eye plaque radiotherapy is an outpatient procedure performed at UC San Diego Health's Shiley Eye Institute.
  • High-dose rate (HDR) techniques for breast cancer. The approach uses high-activity radioactive sources (such as iridium-192). The procedures last only minutes and can be precisely adjusted to customize dose distributions to an individual's anatomy and tumor. HDR is performed at a special suite at Moores Cancer Center and is particularly appropriate for older adults or those with multiple medical problems. The types of HDR techniques we use to treat breast cancer include partial breast irradiation, AccuBoost, Contura, MammoSite and SAVI. (We offer other radiation therapy options for breast cancer, too.)
  • High-dose rate (HDR) techniques for  gynecologicalhead and neck, and skin cancers, as well as sarcomas
  • Electronic brachytherapy with Xoft for non-melanoma skin cancers, most commonly basal cell and squamous cell cancers

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