A specialized type of external beam radiation therapy called stereotactic body radiation therapy (SBRT) or stereotactic ablative body radiotherapy (SABR) uses focused radiation beams targeting a well-defined tumor, relying on detailed imaging, computerized three-dimensional treatment planning and precise treatment set-up to deliver the radiation dose with extreme accuracy.  SBRT refers to the delivery of an entire course of high-precision, tightly-focused radiation therapy in only one to five daily stereotactic radiation treatments over the course of one to two weeks. 

SBRT is typically used to treat small tumors (<5 cm) of the lung, liver, spine, abdomen, pelvis, and head and neck region.  Stereotactic radiation may be useful for other cancers not readily addressed with surgery or conventional radiation therapy. Your radiation oncologists use specialized scans to pinpoint exactly where within the body the tumor target is located.  A customized holder may be used to keep the body perfectly still during treatment.  At times, your radiation oncologist may utilize respiratory gating technology to adjust for patient motion such as during breathing. These techniques allow doctors to give a high dose of radiation to the tumor in a short amount of time. SBRT is a type of external beam radiation therapy that can be completed in one to five days rather than over several weeks.

The advantage of SBRT is it delivers the right amount of radiation to the cancer in a shorter amount of time than traditional treatments. Plus the treatment is delivered with extreme accuracy, minimizing the effect on nearby organs. Finally, the larger doses of radiation delivered during each stereotactic treatment are more biologically effective at destroying tumor cells than conventional radiation doses.  This may allow better rates of tumor control and cure than tradiational radiation therapy. 

Stereotactic body radiation therapy frequently incorporates two other cutting edge technologies in the field of radiation therapy.  Intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT).  IMRT is a three-dimensional radiation therapy treatment that allows radiation oncologists to optimize the planning and delivery of high doses of radiation to targeted areas, while minimizing radiation to healthy tissue. IGRT enhances the accuracy and precision of IMRT by using detailed images to target diseases.

Although there are many stereotactic radiation therapy technologies available, all of these treatments involve:  

• Precise beam shaping and targeting using multiple narrow radiation beams.  
• Target small, well-defined areas with precision.
• Higher doses of radiation delivered safely and accurately.  Because of this precise targeting, radiation oncologists can deliver higher doses of radiation that are more biologically effective at destroying tumors, while sparing the healthy cells surrounding the tumor site.
• Entire treatment course delivered in one to five treatment sessions.  Unlike conventional radiation therapy that involves many treatment sessions scheduled multiple times each week and over the course of many weeks, SBRT is delivered over the course of only one to two weeks. Because the stereotactic approach uses higher and more targeted doses of radiation, fewer sessions are necessary to ensure equal if not superior outcomes.
• Use immobilization devices or techniques that limit monitor and adjust for any movement during treatment.

Although not all patients are candidates for SBRT, your radiation oncologist can tell you whether this approach is an option for your specific condition.

Material excerpted from ASTRO (Copyright © 2011)