SBRT/SABR – Stereotactic Body/Ablative Radiosurgery

Cancer can occur anywhere in the body, and there are many types of therapies to treat specific cancers. Not all cancers can be treated with the same therapies for a variety of reasons, such as location in the body, type of tumor, or factors in the patient’s medical history. Stereotactic Body Radiosurgery (SBRT) is a type of radiation therapy that treats small, isolated tumors in certain parts of the body.

What is Stereotactic Body Radiosurgery?

Example of SBRT dose distribution. Image courtesy of Open-i Biomedical Images.

Stereotactic Body Radiosurgery (SBRT) is a type of radiation therapy which treats certain types of cancers using specialized equipment and X-rays. SBRT is also known as Stereotactic Ablative Radiosurgery (SABR).

Like all types of radiation therapy, SBRT damages the DNA of cancerous cells to prevent them from being able to reproduce and spread. Over time, the tumor becomes inactive, stabilizes, and shrinks.

SBRT is very accurate and results in fewer side effects because less healthy tissue is harmed during the procedure. SBRT uses smaller individual doses over a longer amount of time, which results in a greater combined dose.

Common areas treated with SBRT:

• Liver
• Lungs
• Prostate
• Vertebral bodies

SBRT can only be used on small, isolated tumors only. This treatment method can be used for tumors that move with natural body movement, such as tumors in the lungs.

How does Stereotactic Body Radiosurgery Work?

Stereotactic Body Radiosurgery occurs in several stages. Each stage helps ensure that you receive accurate, quality treatment.

SBRT Planning
A CT or MRI scan is first performed to determine the exact location, size, and shape of a tumor. These scans build a 3-D image of the tumor for optimal accuracy. Your radiation oncologist then works with a skilled radiation team to plan the treatment type and dose using information from the scans. The team may try hundreds of combinations of beam and dose configurations to determine which is best for you.

Some tumors may require a fiducial marker in or near the tumor for image guidance. A fiducial marker is a small piece of metal that helps accurately detect the location of a tumor. In turn, the marker allows the radiation team to deliver the maximum amount of radiation dose to the tumor without harming healthy tissue. You will need a separate appointment and sufficient time for the marker to settle in place prior to SBRT treatment. For lung or liver tumors, a 4DCT scan may be taken to help determine how a tumor moves while you breathe.

Patient Positioning
Mold or casts called ‘immobilization devices’ may need to be created to help you stay in the proper position during treatment. These devices help ensure that the radiation does not damage healthy tissue. A simulation scan will be performed on the day of treatment to verify that the tumor is correctly aligned with the treatment machine and computer calculations.

What to Expect During SBRT Treatment:

• SBRT is performed on a Linear Accelerator.
• An immobilization device may be used to help you remain still.
• There will be a simulation scan on the day of treatment. This scan lines up the tumor with computer calculations and is accurate within 1 – 2 millimeters.
• Once you have been positioned with final scans and guidance from the radiation oncologist, the radiation therapist then delivers the treatment.
• In some cases, scans may be taken during the procedure to monitor the alignment of beams and position of tumor.
• The radiation therapist will be in a separate room controlling the machine. You will be awake and in communication with them the entire time.
• SBRT is painless and you can go home on the same day.

Your radiation oncologist or radiation nurse will advise you of any expected Side Effects and prescribe medication as needed.

Side Effects of Stereotactic Body Radiosurgery

The high degree of SBRT treatment accuracy and minimal exposure to healthy tissue means fewer side effects for patients.

General Side Effects of SABR:

• Fatigue
• Swelling in treatment area
• Soreness in treatment area
• Skin reactions such as redness, dryness, or itchiness

In addition to general side effects, some patients may experience specific side effects. These reactions are usually related to the area which is being treated.

Common Side Effects in the Chest

• Sore throat
• Loss of appetite
• Changes in taste
• Heartburn
• Difficulty swallowing
• Lung problems
• Breast changes

Late term side effects can occur, but these usually manifest years after the final SABR treatment.

Late-term Side Effects of Radiation Therapy in the Chest:

• Heart problems
• Radiation myelopathy (damage to the spinal cord)
• Pulmonary fibrosis (thickening of lung tissue)

Your doctor can answer any questions and discuss all possible short and long-term side effects with you.

How Long Does Stereotactic Body Radiosurgery Last?

Stereotactic body radiosurgery (SABR) usually takes place in 1 – 5 treatment sessions over the course of one or two weeks. Most treatments usually conclude within 10 days. Each session usually lasts 30 minutes – 1 hour.