Stereotactic Body Radiotherapy
Stereotactic Body Radiotherapy (SBRT), is an emerging image-guided radiation method. SBRT is directed to extremely well-defined targets within the body. SBRT will deliver very high doses of radiation precisely to tumor sites within the body with the purpose of improving local control and limiting side effects. SBRT is appropriately used for small lung cancers or metastasis, small isolated liver tumors or bony tumors, and tumors in other sites that may not be appropriate for surgical resection or in patients who would not be candidates for surgery.
SBRT has evolved from the intracranial experience of stereotactic radiosurgery (single fraction treatment) or stereotactic radiotherapy (multiple fractions of treatment). At Virginia Mason, we have been at the forefront of delivering intracranial stereotactic radiotherapy with a frameless system since 1989. Our frameless intracranial system was easily adapted to deliver SBRT. We have been able to deliver SBRT since 2000 for selected cases and have growing experience with this technique.
The fundamentals of the Virginia Mason system are very small implanted markers within the body to provide stereotactic image guidance during radiation therapy. The small markers are gold and are implanted with minimally invasive techniques usually in the radiology department. We utilize 3D imaging (CT, CT/PET, and MRI) and treatment planning to construct very precise plans minimizing radiation doses to normal structures. Treatment with “respiratory gating” is used for tumors in organs that move during respiration such as lungs and liver. SBRT requires complex planning and relatively long treatment times (30-45 min) but generally is completed in 3-5 treatments. SBRT is associated with few side effects because the treatment field is generally very small and treatment is precisely delivered. Side effects that might occur are related to the body site receiving treatment.