Stereotactic Body Radiation Therapy (SBRT)

Stereotactic Body Radiation Therapy (SBRT) is a technique for directing multiple beams of high dose radiation very precisely to a tumor, using coordinates provided by radiologic imaging. This non-invasive therapy delivers photon radiation from numerous angles to focus at one point, similar to a magnifying glass. It is used to treat tumors in the body, most commonly in the lung, liver, pancreas, head and neck region, and spine. The therapy generally involves 1–5 treatments (known as “fractions”) delivered via a high-tech radiation treatment machine called a linear accelerator (LINAC). Patient immobilization is critical for accurate targeting and reproducibility in each treatment.

By using a large number of unique beams that are precisely shaped to deliver the radiation to the tumor, stereotactic radiotherapy minimizes side effects by reducing the dose of radiation to normal organs around the tumor – as only some of the individual beams pass through healthy tissue. Precise targeting of the tumor is required, since the dose of radiation to that single point is so high. The very precise, high dose radiation with Stereotactic Body Radiation Therapy has revolutionized the way we treat many cancers by greatly increasing the chances of eradicating the tumor while minimizing the risk of side effects.

Technical Details

For those seeking a more detailed technical description of SBRT modalities, the following describes techniques commonly performed at our institution: 

  • SBRT is a technique of delivering high doses of radiation to a single target using multiple small beams of radiation over one 1 to 5 treatments. This highly precise, non-invasive therapy is accomplished by a number of different techniques including: rigid immobilization of the patient, referencing the patient’s tumor to an exact coordinate, delivering multiple beams of radiation that concentrate radiation dose in the tumor and results in a sharp fall-off of radiation dose that minimizes radiation exposure to the surrounding organs, and imaging immediately before and/or during the radiation treatment to align the patient’s tumor into the correct position.
  • Advances in imaging technology allow accurate capture of tumor motion through the breathing cycle, which further improves the precision of radiation treatment targeting.
  • The high level of precision allows for the safe delivery of much higher doses of radiation than can be accomplished with conventional fractionated radiation therapy. Whereas conventional fractionated radiation therapy regimens treat tumors using large treatment fields to a total dose of ~60-80 Gy with small daily doses (2 to 2.5 Gy per day) over ~30-35 treatments, the higher doses per fraction and precision of stereotactic body radiation therapy allow safe delivery of radiation doses to the tumor as high as 5-10 times the doses delivered with conventional treatment. This very focal, high dose radiation is often effectively an ablative dose leading to a very high chance of tumor eradication (~90% for many disease sites), while minimizing the risk of injury to surrounding organs.
  • Since the treatment can be given in as few as 1 to 5 treatments, with each treatment usually given one to two days apart, patients can complete their stereotactic body radiation therapy course in just 1 to 2 weeks, which is much more convenient than the 6-8 week course of treatment with conventional fractionated radiation therapy.
  • This technique has revolutionized the way we treat many cancers, including tumors involving the lung, pancreas, liver, spine, and head and neck region, and is particularly useful for treating patients for whom no options were previously available, including patients who are not candidates for surgery and patients who have already received prior radiation therapy.

Innovative Applications

Our team is constantly exploring innovative uses of advanced technologies to achieve improved patient outcomes. Here are two of the innovative protocols we are currently investigating with SBRT:

Combining Immunotherapy with SBRT
Lead physician: Jonathan Schoenfeld, MD, MPH 

Experiments suggest that radiation may stimulate the immune system and help immune therapies work better to kill cancers throughout the body in both the areas that have received radiation and in other areas as well. This ongoing research is testing whether using SBRT to kill cancer cells can produce a vaccine-like effect and improve the likelihood of response as compared with immunotherapy alone. 

Using SBRT to Treat Cancer that has Spread to the Bone
Lead physician: Tracy Balboni, MD, MPH 

Cancers frequently involve the bone, where it can cause symptoms such as pain or fractures, or induce weakness by affecting nearby nerve structures. SBRT can treat bone tumors in a manner that is both dose intense to optimize tumor ablation and prevent recurrence, while being highly focused to avoid nearby normal tissues. This ongoing research is examining the efficacy of SBRT to treat tumors that have spread to bone, including outcomes of bone tumor control, patient symptoms and quality of life. 


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